The night before you plan to make the tart, place a fine mesh sieve over a small mixing bowl and line it with a paper towel. Measure out the Greek yogurt into the sieve, cover with plastic wrap, and let sit in the refrigerator overnight so all of the liquid strains out.
The next day, preheat the oven to 350 degrees Fahrenheit and spray your tart pan with nonstick cooking spray. Set aside.
Combine all of the crust ingredients in a large mixing bowl using your hands. Keep working it until a crumbly dough forms, then press the dough into the prepared tart pan, doing your best to keep everything even and make sure there aren’t certain parts that are thinner than others. You want the dough to extend up all the way to the top edges of the tart pan all the way around.
Place tart pan on a pizza sheet or large baking sheet (to catch any butter/grease that leaks out of the pan), and bake in the oven for 10-12 minutes, or until the crust takes on a nice golden color. Remove and let cool completely.
Next, dump the water that strained off of the yogurt out of the small mixing bowl and use it to make the filling. Add the strained yogurt, almond extract, lemon zest and powdered sugar and stir until well-combined.
Scoop the filling out into the cooled tart shell and, using the inverted spatula, spread it around evenly.
Top the tart with the strawberries and raspberries, then sprinkle on the julienned mint and slivered almonds. Serve as soon as possible and store in the refrigerator if you don’t finish it all in one sitting!