01 -
Heat oven to 175°C / 350°F. Grease and line a 20 cm square pan. Dice the peeled apple into pieces about 7 mm across. Keep 80 g butter softened and melt the remaining 30 g.
02 -
For the crumb topping, mix 40 g flour, 40 g brown sugar and ½ teaspoon cinnamon. Stir in the 30 g melted butter with a fork to make coarse crumbs. Set aside.
03 -
Whisk the remaining 180 g flour with baking powder, baking soda, salt and remaining 1 teaspoon cinnamon. In another bowl, beat the 80 g softened butter with remaining 100 g brown sugar until creamy.
04 -
Beat eggs into the butter mixture one at a time, then add vanilla. Fold in half the dry mixture, the sour cream, then the rest of the dry mixture. Gently fold in all the diced apple.
05 -
Spread batter in the pan and scatter the reserved crumbs evenly on top. Bake 38–45 minutes until the center springs back lightly and a skewer comes out without wet batter. Cover loosely with foil if the crumbs brown too quickly.
06 -
Cool in the pan on a rack for 45 minutes before lifting out and cutting into nine squares. Serve without icing; coffee cake means a cake served with coffee, and this recipe contains no coffee.
07 -
Keep covered in the refrigerator for up to four days. Bring portions briefly toward room temperature or warm gently before serving. Freeze individual squares for up to two months.