I have a culinary conundrum for you. It's one I've been pondering for a long time now, often while daydreaming in the swimming pool or on my bike. Yes, I know that's a bit dangerous.

Why is it that some flavours taste more of themselves than the actual ingredient they have derived from?

That probably doesn't make any sense. Let's take an example.Marzipan.

Marzipan has that distinctive almond flavour, the kind you find in macaroons and flavoured sweets or chocolate. The kind you find in those mass-produced, impossibly neat, garish bakewell tarts with a cherry on top.

OK, so you've eaten almonds, right?

They taste nothing like almonds.

Almonds have a strange, mouth-puckering dryness. They're soft, crumbly, and have a very very subtle sweetness and a deep, earthy flavour. But they bear no resemblance in taste to anything that carries their name. Almond croissants. Almond marzipan. Almond macaroons. Almond cakes. These things taste how we expect them to taste; they taste of the flavour we have come to associate with almonds. I've used ground almonds in cakes many a time, and found they impart little or no flavour to the rest of the cake; they certainly don't pack an almond punch on their own, whether whole or crushed up.

How, then, do they derive this flavour from a nut that tastes nothing like that? And why do we accept this unnatural and bizarre notion of almond flavour?

It's the same with coconut. Actual coconut flesh tastes almost nothing like the synthetic 'coconut' flavour we put in baked goods and chocolates, in Bounty bars and coconut ice and other tropical delights. It's remarkably subtle in taste, as is the coconut milk we add to curries and are often disappointed with because it doesn't offer enough of a 'coconut' hit, enough of that artificial flavour we've come to associate with coconut.

I'm sure some molecular gastronomic genius like Harold McGee or Heston Blumenthal would be able to answer me on this, but if anyone else (Heston, I know you're busy - please don't feel like you have to comment on all my blog posts) has an answer to this serious query of mine, there's a comment box at the bottom of the page.

But obviously you don't care about my almond and coconut dilemmas, because what you really want to know is how damn good this cake is.

Doesn't it just look the picture of rustic, English perfection? I can't think of a more traditional tea-time cake than this. It uses quinces, a medieval fruit that has sadly fallen out of favour yet, for me, is one of the most exquisite ingredients in the world. It has a complexity of flavour like no other; I once made a sorbet that contained just quinces, sugar and water, yet from its taste you would have thought it was spiked with a heady cocktail of fragrant spices.

Indeed, when my father tried this cake he was adamant that I'd put cinnamon in it. I hadn't. That's just the complexity of quince for you; it has a perfume redolent of mulled wine and potpourri and the bubbling cauldrons of medieval cooks, brimming with treasures from the spice trail.

Poached quince segments make a great basis for all sorts of desserts. By simply simmering them in the gentlest possible way, in a syrup of sugar and water flavoured with whatever herbs and spices you choose, you end up with kitchen gold - literally. They mellow and soften, becoming golden, sometimes deep sunset red, full of ambrosial fragrant flavour and with a pleasant yielding yet grainy texture not unlike that of a perfectly ripe pear.

Cooked like this, you can use quinces for so many things. I like them pure and simple, spooned onto my morning porridge with a handful of tart blackberries or blueberries. They are also excellent with ice cream, or you can use them to top a dessert, as in this wonderful quince tarte tatin recipe. Cover them in pastry for a beautiful pie, or top with a coarse crumble for a buttery treat.

Quinces marry particularly well with almonds. Given that they are not dissimilar to pears in both shape and texture when cooked, this shouldn't be surprising. The idea to include them in a cake with marzipan came to me when I was baking mini simnel cakes this Easter. I had some high-quality marzipan to use up, and some quinces sitting in the fridge, and I suddenly thought that stirring cubes of marzipan into a cake batter with cubes of poached quince would create something fabulous.

I wasn't wrong; this is a beautiful cake. The cubes of marzipan melt in the heat of the oven, giving a gorgeous gooey texture and sharp hit of almond flavour (that strong, almost fake variety, as discussed at the beginning of this post). The quince is soft, grainy and fruity, delivering a sweetness and a perfume that matches beautifully with the marzipan. The cake is nutty from the use of spelt flour and the scattering of flaked almonds over the top, resulting in a dense crumb that is beautifully moist from the molten marzipan and the juicy quince.

This isn't a very sweet cake; it's more of a pudding to be eaten after a light meal, or something to be served in slabs with a good cup of afternoon tea. The quince and marzipan combination is more than enough sweetness for the whole cake, so there isn't much extra sugar involved. I'd suggest pairing it with vanilla ice cream, as the cold cleanliness of the ice cream is a good foil for the sugary marzipan and the fragrant quince. If you don't have quinces (they're quite hard to find even when in season), use ripe but firm pears - but don't bother with the poaching step, just cut them up and put them in raw.

This is a hearty, rustic cake, the kind I can imagine a medieval chef unearthing from the bowels of the oven and cutting into thick slices to serve after a banquet of venison and wild fowl. It looks beautiful and makes a satisfying pudding or afternoon treat, the kind of thing that will keep you going in that hideous destitute period between lunch and dinner when all seems bleak.

Pair it with a strong cup of tea - perhaps something rich and smoky like lapsang souchong - or coffee, cut yourself an indecently large slice, and savour the comforting, crumbly warmth of the cake and the surprising burst of gooey marzipan pieces. This is a proper cake, as cakes should be.

Quince and marzipan cake (serves 8-10):

600ml water
250g caster sugar
1 lemon
All or a mixture of: cloves, star anise, crushed cardamom pods, cinnamon stick, vanilla pod, bay leaf
3 medium quinces [Or, if you can't find quinces, just use 4-5 ripe but firm pears - Conference are good - and skip the rest of the above ingredients]
310g spelt flour (or plain/wholemeal, depending on your preference)
1 tbsp baking powder
80g brown sugar
Grated zest of 1 lemon
1/2 tsp salt
60g melted butter, cooled slightly
2 eggs
340ml buttermilk (or yoghurt loosened with a little milk)
150g marzipan, cut into 1cm cubes
2 tbsp flaked almonds

First, prepare the quinces. Bring the water and caster sugar to the boil in a large saucepan, then bubble away for a couple of minutes so the sugar dissolves. Cut the lemon in half and add to the pot. Add your chosen herbs and spices. Peel the quinces then cut into quarters. Remove the tough core and cut each quarter lengthways so you have eight slices. Add the quince slices to the liquid. Top up with more water, if necessary, so they are just covered.

[If using pears, skip this step and go straight to the cake-making - cut up the pears as below and use them raw]

Cut a circle of greaseproof paper to fit over the quinces in the pot, and cut a 1-inch hole in the centre. Place over the quinces, touching the water, then turn the heat right down. Simmer very gently for an hour or so, until the quinces are tender but still holding their shape - check them occasionally as you don't want them disintegrating. Remove with a slotted spoon and place on a chopping board. Slice three or four of the segments lengthways into three pieces so you end up with long, slender slices. Cut the rest of the segments into 2cm dice, and set them all aside to dry on a piece of kitchen towel.

Pre-heat the oven to 190C (fan oven). Grease a 25cm cake tin or fluted tart tin and line it with baking parchment.

Sift the flour and baking powder into a large bowl. Add the brown sugar, lemon zest and salt.

In another bowl whisk together the melted butter, eggs and buttermilk. Pour this into the dry mixture and fold together gently with a large spoon until just combined - don't over mix.

Fold the cubes of quince and marzipan into the mixture so they are evenly dispersed. Pour the mixture into the prepared tin, then arrange the long quince slices in a pattern over the top of the cake. Scatter over the flaked almonds.

Bake in the oven for 35-40 minutes until the centre is firm and a skewer comes out clean. Leave to cool slightly before dusting with icing sugar.

Serve with vanilla ice cream. It's best eaten warm, but keeps for days wrapped in foil and reheats well in the oven or microwave.