Versavisa - no, they don't rise to a think point, more like dome-shaped.
I don't usually give away my secret recipes but just betwen you and I, try:
100g margerine
100g caster sugar
2 eggs
100g self-raising flour
Few drops of vanilla essence
Lime or lemon juice (freshly squeezed after you have zested it first)
Lime or lemon zest
Beat marg and sugar until it changes colour (becomes paler) and very, very creamy in texture. Whisk eggs. Add a very small amount of the flour to the mixture and add some of the beaten egg and beat the eggs into the mixture - repeat until eggs have been incorporated. Gently fold in the flour in two goes. Add the vanilla essence and fold again. Add the lime or lemon juice. Mixture should be a soft dropping consistency (if you have to shake it off the spoon, you can add a little bit of milk). Spoon into paper cases (I tend to use muffin paper cases).
Bake at around 180 (you know if your own oven bakes hot or cooler so adjust accordingly if it does) for around 15 mins (but keep an eye on them. You can touch the top to see if they're spingy when checking if they're cooked but you can also check by looking underneath the cake case and the sponge should look cooked.
Filling
Depending on how many cakes you have made and how much buttercream you like will determine quantity but a starting point is:
200g of butter or margering
500g of icing sugar
Lime or Lemon juice
Grated zest of lime or lemon (how much depends on your taste for it)
Mix the icing sugar and marg and beat the living daylights out of it. Beat in the juice. Add the zest and stir - buttercream should be soft but not too runny (not thick either!).
When cakes have cooled, using a sharp, pointy knife, carefully cut a circle of cake out of each cake (about the size of a 10p) to a depth of about an inch to an inch and a half depedening on the size of cakes you have made (this will produce a thin pointy end thinking about it - you can always replace this upside down onto the cake) and put to one side. Place a level teaspoon of good quality lemon curd into each cake and top with lime/lemon buttercream; replace the removed piece of cake and push down gently so that buttercream oozes out slightly. Dust lightly with icing sugar.
If you take them to car boot sales, they sell very quickly if you bring them here, they'll disappear even quicker!
I hope they come out the way you are looking for