In a large skillet, heat 1 tablespoon of olive oil and sauté onions, peppers, and garlic until crisp-tender.
Add spinach and sauté until wilted, then remove from heat.
Whisk together eggs, ¼ cup olive oil, and Greek yogurt in a mixing bowl.
Add flour, baking powder, salt, feta, mozzarella, dill, and vegetable mixture to the bowl. Mix well.
Spread the batter into a loaf pan lined with parchment paper.
Bake at 350°F for 50-60 minutes until done.
Allow the loaf to cool before slicing and serving.