Savory Apple Tart Recipe with Thyme, Caramelized Onion & Gruyere

1 batch store bought or home made pie dough 1 roll of store bought pie dough is enough for two individual 6 inch tarts
1 tablespoon unsalted butter
1 tablespoon olive oil
1 small yellow onion sliced into thin rings
½ cup crème fraîche
1 teaspoon Dijon mustard
1 cup shredded Gruyere cheese
½ tablespoon fresh thyme leaves chopped, plus more for garnish
1 apple cored and thinly sliced
Salt and freshly ground pepper
On a lightly floured surface, roll out the dough and press into two six-inch tart pans, trimming off excess. Refrigerate until firm, about 30 minutes.
Preheat oven to 375°. Line the dough with parchment paper and top with pie weights or dried beans. Bake for 20 minutes. Remove the parchment and weights. Continue baking until the crust is golden brown and crisp, about 10 minutes more.
Transfer tart pans to a wire rack and let cool slightly. Reduce the oven temperature to 350°.
Meanwhile, make the filling: In a skillet over medium heat, melt the butter with the olive oil and swirl the pan to combine. Add the onions and cook until lightly browned and starting to caramelize, about 8 minutes per side. Remove from heat.

In a small bowl, stir together the crème fraîche and mustard and spread evenly over the crust. Sprinkle with half of the cheese and the thyme. Arrange the apple slices and onions on top. Sprinkle with the remaining cheese and season with salt and pepper.
Bake on the top oven rack until the pastry is golden and the cheese is melted, about 15 minutes. Let cool for 10 minutes, then garnish with thyme, cut into slices and serve.

Recipe Notes
No pie weights for blind baking? No problem! Use sugar instead (here's a how-to) ! This method comes with a bonus: faintly caramelized granulated sugar - the best for baking banana bread!
Use a wide skillet for caramelizing the onions. This gives the water room to evaporate, allowing the onions to caramelize rather than steam.
If you feel like onions are getting too brown around the edges reduce your heat a bit.