Pre-heat the oven to 350 °F
Spray a mini tart pan with nonstick spray
Make the dough for the crust: whisk together the flour, granulated sugar, and salt. Using an electric mixer, add the butter and the egg yolk
Wrap the crust dough in plastic wrap and put it in the fridge for a couple of hours.
Take the tart dough out of the fridge and let it soften up at room temperature for about 20 minutes.
On a flour-covered surface, roll the tart dough out with a rolling pin. We'll want to roll it quite thin, about ⅛" thickness
Cut 12 circles of dough with the cookie cutter (you might need to re-roll the dough a few times to get your 12 circles)
Arrange the 12 circles in the 12 cavities of your tart pan, being sure to press the dough down into the cavities.
Bake the tart shells in the oven for about 10 minutes
Stir together the yogurt, maple syrup and vanilla extract. Spoon about 2 tablespoons into each baked tart shell, and top with fruit.