Preheat the oven to 350F/180C.

Combine the corn meal, semolina, flour, salt, baking soda, baking powder and turmeric in the bowl of an electric mixer. Spin at low speed to combine. Set aside.

Heat 2 tablespoons olive oil in a large heavy frying pan and cook the onions over medium heat until wilted. Remove with a slotted spoon.

In the same frying pan, add the diced zucchini and sauté until lightly browned and slightly softened, just for a few minutes, careful not to overcook the zucchini lest it become mushy. Season it with a pinch of salt as you sauté.

Let the onions and zucchini cool slightly.

Whisk the eggs, milk and yogurt together and pour into the dry ingredients. Using the paddle attachment, stir into the dry ingredients at medium speed, until the mixture becomes a thick, dense batter. Add the zucchini and onions, the mint, fennel, black pepper and additional salt to taste. Gently stir in one cup of the feta.

Oil two 10-inch / 22.5 cm X 3-inch / 7.5-cm-deep loaf pans. Pour in the batter.

Sprinkle the remaining feta cubes over the surface of each loaf. Bake in the lower third of the oven for about 45 to 55 minutes, until golden and set. Remove, cool slightly, and turn each loaf onto a rack to cool completely.