1 cup packed light brown sugar
2 cups all-purpose flour
1/2 teaspoon baking soda
1/4 teaspoon salt
2 cups rolled oats
1 cup butter, softened
14 oz. guava paste (more or less, depending on how thick you like your fruit layer)
Preheat oven to 350 degrees F.
Grease a 13x9-inch pan, and line with foil or parchment paper. Lightly grease paper/foil.
Combine brown sugar, flour, baking soda, salt, and rolled oats. Cut in butter with a pastry blender or two knives until mixture is crumbly.
Press 2/3 of the crust mixture into the prepared pan. Slice the guava paste into enough pieces to cover the crust within 1/4 inch of the edge, and place in pan. Sprinkle remaining crust mixture over guava paste layer.
Bake for 35-40 minutes in preheated oven, or until crust is lightly browned. Allow to cool in pan on wire rack before cutting into pieces and serving.