Fluffy and Airy Plum Upside Down Cake with a twist

Plum upside down cake is a favourite in our family. I can't remember where the recipe initially came from but I remember making this cake since I was a teenager and although it goes well with various soft fruit - as apricots and peaches - and even had as apples my most favourite one is with plum.
I like everything about this cake - the caramel pieces that go inside the sponge while baking, the aromatic plums scenting the cake with their perfume and releasing their tangy sweetness, the sponge - sometimes contrasting with more biscuit-like texture and sometimes accompanying with matching softness (like today) - it's a delight.
The recipe I am usually using is more dense and I wanted something airier and fluffier and definitely lighter (not in the sense of having less calories) to try this time. The result was very successful - the lime flavour in the sponge matching and complementing the taste of the caramelised plums nearly to perfection.
So I am happy to share this delightful dessert which we shamelessly ate as a breakfast enjoyed with our teas/coffees. (Yes, all of us!)

Airy Plum Upside Down Cake 

(Makes one 8 inch cake)

to line the cake tin:

1/2 cup sugar for caramelising 

5-6 (depending on the variety and size) ripe but still firm plums sliced

for the sponge:

2 small eggs

80 g butter

1/2 cup sugar (100 g)

90 g self raising flour

25 g shredded coconut 

2 drops lime essence or 1 tsp lime juice

Method:

Heat the sugar in the tin on low heat and turn and mix until the bottom of the cake tin is covered in smooth caramel. Remove from heat and arrange the sliced plums.

In a bowl beat the butter with the sugar for about (less than) a minute. Add the eggs and mix for a few seconds more until blended. With a spatula incorporate the coconut and flour. Finally add the lime extract drops. (I have to add here that I am very happy to fins lime extract - the flavour it gives is natural and intense.)

Bake at 180 C (170 C fan) oven for 30 minutes. Leave to rest for some 5 minutes, then turn upside down until hot.