For the shells: Pulse together the granulated sugar, flour and salt in a food processor to combine. Add the butter and continue to pulse until mealy. Add the egg yolks (reserve the egg whites for the filling) and pulse until the dough comes together. Press the dough into a disc, then wrap in plastic wrap and refrigerate for at least an hour, or up to overnight.
To mold the shells, grease a muffin tin with nonstick spray. Roll out the dough on a floured surface to 1/4-inch-thick, dusting with more flour as needed. Cut out 3-inch circles and press them into the muffin cups so that the dough comes all the way up the sides. (No worries if the dough tears; just patch it up with additional dough.) Freeze the shells for 15 minutes.
For the filling: Preheat the oven to 350 degrees F.
Combine the almond meal, granulated sugar, salt, and butter, either by blending it in the food processor (no need to clean it out after making the dough, you can just use it immediately for this step), or by stirring it together in a large bowl (I find it's easiest to get in there with my hands). Add the almond extract, egg and the reserved egg whites from the shells, and continue to blend/stir until smooth and combined.
Fill the frozen shells with the filling so that it comes up about 1/4-inch from the top. Bake until the tops and edges are lightly browned; begin checking for doneness at 30 minutes. Let cool in the pans for 10 minutes, then use a small offset spatula or a knife to remove to a wire rack to cool completely.
For the glaze: If making the glaze with heavy cream, combine the powdered sugar, heavy cream and almond extract in a bowl until smooth. Add additional powdered sugar or liquid to thicken it up or thin it out so that you get the consistency of a thick glue.
To make the glaze with the raspberries, place the raspberries in a fine-mesh sieve and give them a rinse. Place the sieve over a bowl and use a stiff rubber spatula or wooden spoon to smash them through the sieve into the bowl until you're just left with seeds in the sieve. Be sure to scrape the underside of the sieve to get the stuff that's sticking to it. (You should be left with about 2 tablespoons seedless puree. If it's a tiny bit more or a tiny bit less, that's fine.) Add the powdered sugar and almond extract and mix to make a thick glaze. If it's too thick, add a few drops of water to thin it out, and if it's too thin, add a few more spoonfuls of powdered sugar. It should be the consistency of a thick glue.
Spread the glaze over the cooled tarts and decorate with sprinkles, almonds and anything else you'd like! These will keep for several days at room temperature or in the fridge.