Heat oven to 350°F. Grease an 8-inch square pan with cooking spray.

In a medium bowl, mix together 2/3 cup butter, white sugar, and flour until evenly crumbly. Reserve 2 tablespoons of the dough for topping. Press the rest of the dough into a prepared pan. Bake for 15 minutes.

Remove from oven and spread the jam on top. Crumble the reserved dough on top. Sprinkle with almonds if using.

Return to the oven and bake until the edges are golden brown, 20 more minutes.

Let cool completely before cutting. Once cool, sprinkle with powdered sugar if using. Cut into 16 bars or triangles.