Preheat oven to 350ºF.

Line an 8” square pan with parchment paper or lightly butter a folding-edge silicon pan.

Place butter in a large microwave-safe bowl and heat in the microwave until melted. Whisk the sugars into the butter and add the vanilla. Add flour, oats, and salt and stir to combine.

Reserve 1 rounded cup of this mixture for topping.

Press the remaining mixture evenly into the prepared baking pan.

Spread the 1 cup of preserves evenly over the base, right to the edge.

Sprinkle the reserved cup of crumb mixture evenly over the jam.

Bake for about 30 minutes or until the edges are set, and the top is lightly golden.

Place the pan on a wire rack and cool for at least 2 hours before cutting it into squares. If using a silicon pan, slide the entire square onto a cutting board before slicing or use a plastic knife to avoid damaging the pan. Serve or freeze for later.