Preheat and Butter Pan:

Heat the oven to 350°F (175°C). Butter a 9-inch springform pan or a 9x13-inch baking dish.

Cook Onion and Scallions:

In a skillet over medium heat, warm 2–3 tablespoons olive oil. Add the onion with a pinch of salt; cook until soft and lightly browned. Stir in the scallions and cook 2–3 minutes until tender. Take off the heat.

Whisk Dry Ingredients:

In a bowl, combine flour, baking powder, and salt by whisking.

Mix Wet Ingredients:

In another large bowl, whisk olive oil, milk, yogurt, and eggs until smooth.

Combine Wet and Dry:

Pour the dry mixture into the wet mixture and stir just until incorporated.

Fold in Mix-Ins:

Gently fold in olives, feta, parsley, and the cooked onion mixture.

Pour Batter and Top:

Pour the batter into the prepared pan and smooth the top. Sprinkle generously with sesame seeds.

Bake Until Done:

For the 9x13-inch pan, bake approximately 25 minutes until a toothpick inserted in the center emerges clean or with a few crumbs. For the springform pan, bake about 50–55 minutes until golden and a toothpick inserted in the center comes out clean.

Cool and Serve:

Let cool before unmolding. Slice and serve.