Instructions:
- Preheat oven to 350°F (175°C). Grease or line an 8×8 inch (20×20 cm) baking pan.
- Mix dry ingredients: In a bowl, combine flour, powdered sugar, baking powder, salt, and lemon zest (if using).
- Cut in butter until mixture resembles fine crumbs.
- Add wet ingredients: Mix in egg yolks, sour cream, and vanilla. Knead gently until a soft dough forms.
- Divide dough: Split into two portions (1/3 and 2/3). Chill smaller portion for lattice.
- Press 2/3 of dough into the bottom of the baking pan evenly.
- Spread jam over the dough in a generous layer.
- Roll and slice the remaining dough into strips and arrange in a lattice pattern over the jam.
- Bake for 25–30 minutes or until lightly golden.
- Cool and slice into squares or bars. Dust with powdered sugar if desired.
Tip: Best after a few hours once the jam sets — just like grandma used to make!
Let me know if you’d like a chocolate-filled version or a gluten-free twist!