Swedes love cardamom in their baking and this recipe is a typical fika treat. You can use whole cardamom seeds that have been crushed if you don't mind little crunchy bits in your cake, or ground cardamom if you prefer a smooth sponge.

150g butter
3 egg yolks, room temperature
1/4 c brown sugar
3/4 c flour
4 tsp crushed cardamom seeds or 2 tsp ground cardamom
3 tbsp lemon juice
1/4 tsp salt
3 egg whites
3/4 c natural cane sugar

Extras if desired:
2 tbsp jam
whipped cream

Preheat oben to 175C. Grease and flour a 20cm round cake tin.
Melt butter in a small saucepan. Remove from heat and allow to cool.
In a bowl whisk the egg yolks with the brown sugar until frothy. Pour in cooled butter and whisk together. Sift in flour and cardamom and salt and mix in with the lemon juice until batter is just combined.
In a separate bowl whisk the egg whites until soft peaks form. Add sugar gradually and keep whisking until stiff peaks form. 
Fold meringue mixture into batter until evenly blended. Do not overstir. Pour into your cake tin.
Bake for around 40 minutes until cooked through, using the skewer test. Cover the cake with foil halfway through baking if top is starting to brown too much.
Remove from oven and let cool for 10 minutes before turning out and cooling on a wire rack.
Once cool slice cake into 2 equal layers. Place bottom layer on your serving plate. Spread jam on the cut sides. Spread whipped cream on bottom layer and put the other layer on top. Dust with icing sugar.