Whisk together flour, salt, smoked paprika and turmeric in a large bowl.

Add shortening and butter, and use your fingertips to combine until mixture is pebbly and resembles coarse meal.

Stir in egg and 1/4 cup plus 3 tablespoons cold water and use a fork to stir until dough holds together (it will be fairly stiff).

Use your hands to knead dough together (on a lightly floured surface or even in the mixing bowl).

Divide dough in half, wrap each half in plastic; and then refrigerate for at least 1 hour.

Meanwhile, heat olive oil in a large skillet over medium-high heat.

Add onion, bell peppers, salt and pepper, and cook, stirring, until softened, about 5 minutes.

Add garlic and oregano, and cook until fragrant, about 1 minute. Remove from heat and set aside (this mixture can be refrigerated for a day in advance).

Preheat the oven to 375°F and line 2 baking sheets with parchment paper.

Roll out the dough, dusting the work surface and rolling pin with flour as needed, to 1/8-inch thickness.

Cut the dough into 6-inch diameter circles. Gather scraps and reroll them into additional circles.

Combine onion-pepper mixture with chopped greens and feta.

Place about 2 1/2 tablespoons of vegetable filling in the center of each circle, leaving 1/2-inch border on all sides.

Brush the border with water.

Fold the circle over filling, creating a half-moon. Use the tines of a fork to press the edges together and seal.

Make a few small slits on top of each empanada to allow steam to escape.

Transfer empanadas to the prepared baking sheets.

Whisk together egg yolks with 2 tablespoons of water.

Brush tops of empanadas with yolk mixture and top with a scattering of sunflower seeds.

Bake until pastry is golden brown, about 30 minutes. Serve warm or at room temperature.