To prepare crust: Combine whole-wheat flour, all-purpose flour, thyme (or oregano), salt and 3/4 teaspoon pepper in a bowl. Make a well in the center and add 1/3 cup oil and 5 tablespoons water. Gradually stir the wet ingredients into the dry to form a soft dough. Knead on a lightly floured surface until the dough comes together. Wrap in plastic and chill for 15 minutes.

Preheat oven to 400 degrees F. Coat a 9-inch tart pan with removable bottom with cooking spray.

Roll the dough into a 12-inch circle on a lightly floured surface. Transfer to the prepared pan and press into the bottom and up the sides. Trim any overhanging dough and use it to patch any spots that don't come all the way up the sides. Prick the bottom and sides with a fork in a few places. Bake the crust until firm and lightly brown, 20 to 22 minutes. Let cool on a wire rack for at least 10 minutes.

To prepare filling: Meanwhile, heat 2 teaspoons oil in a large skillet over medium heat. Add chard stems and cook, stirring, until just tender, about 2 minutes. Add garlic and cook, stirring, until fragrant, about 15 seconds. Add chard leaves and 2 tablespoons water and cook, stirring, until the leaves are just tender and the water has evaporated, 2 to 5 minutes. Transfer the greens to a sieve over a bowl and let drain and cool for 5 minutes. Whisk eggs, ricotta, lemon zest and 1/8 teaspoon pepper in a large bowl. Fold in the greens, olives and feta. Pour the filling into the crust. Bake the tart until the top is lightly browned and a knife inserted in the center comes out clean, 30 to 35 minutes. Let cool for 10 minutes before cutting into wedges.

Store at room temperature for up to 2 hours.

9-inch tart pan with removable bottom