CRUST AND TOPPING:
Use any variety of fruit preserves you like or happen to have on hand.
Butter a 9-inch square baking pan and dust it with flour, knocking out the excess, or line it with parchment paper, leaving a 2-inch overhang on two sides.
For crust and topping: Put the almonds and ¼ cup of sugar into a food processor and pulse to a coarse meal. Transfer to a mixing bowl and add the remaining ½ cup of sugar, cornmeal, and salt. Stir. Add the melted butter and vanilla and stir well. The mixture will be damp but crumbly. Transfer slightly more than half of the mixture to the pan. Spread it evenly, then use your fingers to form a level layer on the bottom with a lip extending about ¼ inch up the sides of the pan. Refrigerate for 10 minutes. Preheat oven to 350°F.
For filling: Stir the preserves, then drop by spoonfuls over the crust. Spread the preserves evenly with the back of the spoon. Spread the remaining crumb mixture evenly over the preserves. Tamp down gently with your fingers to compress slightly. Bake on the center oven rack for 25 minutes, until light golden brown. Cool on a rack. Refrigerate for 1 to 2 hours. Serve at room temperature.