1. Make the topping by mixing the flour, brown sugar, almond paste, sliced almonds, almond extract (if using), and butter with your fingers, or a pastry blender, until the pieces of almond paste and butter are the size of kernels of corn. Preheat the oven to 375ºF (190ºC).
2. Pit and halve the apricots and slice them into 1/2-inch (1.5cm) slices. Stem and pit the cherries, and halve them. Toss the apricots and cherries in a bowl with the cornstarch and granulated sugar, and spread the fruit into the baked tart shell.
3. Strew the marzipan topping over the fruit and bake until the top is golden brown and the fruit is bubbling around the edges, 30 to 40 minutes.
(I’ve not had this tart run over, but if you’re the cautious type, you can bake it on a foil-lined baking sheet, in case there are any spills.)
4. Remove from the oven and let cool a bit before serving. Serving: The tart can be served just as it is, warm or at room temperature. It can be accompanied by ice cream, such as vanilla ice cream, whipped cream, or sabayon.