Ingredients:

Shortbread Crust:
1 stick butter at room temp
1/4 cup sugar
1/2 tsp salt
1 cup flour

Toppings:
Approx. 10 ounces guava paste sliced to about 3/16″ thick slices.
Seedless strawberry or raspberry preserves
1/2 cup old fashioned oats
1/2 stick butter
1/2 tsp salt
1/4 cup light brown sugar
1/2 cup flour

Directions:
Line an 8 x 8 square glass pan with parchment paper large enough to go up the sides with a slight overhang for easy removal from the pan later. Adjust oven rack to middle position and preheat oven to 350 degrees.
For the crust, beat butter and sugar together until fluffy. Add salt and flour, mix until dough comes together.
Press dough into prepared pan. A bit of extra flour will help if the dough is sticky.
For the toppings: cover dough with slices of guava paste. Brush about 1/8 cup of preserves over the top of the guava paste.
In a large bowl, combine oats, 1/2 stick butter, salt, brown sugar and 1/2 cup flour. Cut into very fine mixture with pastry cutter, or prepare mixture in a food processor until mixture resembles wet sand with some bigger chunks of crumble throughout. Sprinkle evenly over the top of the pan.
Bake until top is golden brown, about 40-45 minutes. Let cool completely before slicing into squares.