A family classic from the 1990s that is traditionally served in the morning with coffee, but great, well, anytime you have a coffee.

flour, all purpose: 215 g/1.5 cups
baking powder: .75 tsp
baking soda: .75 tsp
salt: .5 tsp
sugar: 170 g/.75 cup
butter, unsalted: 85 g/6 Tbsp/.75 stick
eggs: 2
sour cream: 150 g/.75 cup
apple: 2 large eating apples (e.g. Braeburn, Fuji, McIntosh), cored, peeled, diced medium size, about .375 in/1 cm
pecans: 60g/.5 cup, finely chopped
light brown sugar (UK: muscovado): 95 g/.5 cup
ground cinnamon: 1 tsp
butter: 60 g/2 Tbsp

Heat oven to 175 C/350 F.
Grease an 8″/20 cm square pan with butter or baking spray.
Combine dry ingredients. Sift together flour, baking soda, baking powder, and salt.
Combine wet ingredients. In a mixing bowl, cream together sugar and butter until light and fluffy. Add in the eggs and vanilla and continue mixing on medium speed until well combined, about 1 minute.
Combine wet and dry ingredients. With the mixer running, slowly add both flour mixture and the sour cream. Stop the mixer and add the apple pieces and stir by hand to incorporate.
Make the cinnamon-nut mixture. Melt the butter and remove from heat. Stir in the nuts, brown sugar, and cinnamon.
Prepare the final mixture. To the baking pan, add half of the mixture and spread to be level in the pan. Then, add half of the cinnamon-nut mixture in small spoonfuls–you do not need to spread around. Add the remaining cake batter and level again. Finish by adding the remaining cinnamon-nut mixture on the top.
Bake for 35-40 minutes, until cake is firm to the touch in the middle of the pan. Note that the mixture will be loose due to the apple and sour cream–this will solidify further when cool. Allow to cool completely. Store at room temperature in an airtight container