To a food processor, add the flour, salt, and cubed butter. Pulse until the mixture looks like small peas.

In another bowl, whisk together the sour cream, lemon juice, and water. Add this to the flour mixture and continue pulsing until a dough forms.

Turn the dough onto a lightly floured surface and form it into a smooth ball. Wrap it in plastic wrap and refrigerate for at least 30 minutes.

While the dough is chilling, make the filling. In another bowl, add the ricotta, Parmesan cheese, thyme, salt, and pepper. Stir well.

Preheat the oven to 400°F and chill the ricotta mixture until the oven comes to temperature.

When ready, roll the dough out onto a floured surface into a 13-inch circle and transfer it to a lined baking sheet.

Spread the ricotta mixture onto the dough, leaving a border, and layer the zucchini slices on top.

Fold the dough border over and brush the top of the galette with olive oil. Garnish the zucchini with more grated Parmesan cheese and fresh thyme leaves.

Bake the zucchini galette at 400°F for about 45-50 minutes, until the crust is golden brown.