In a large bowl, combine the crumbled feta cheese, plain yogurt, eggs, and baking powder.
Mix well until the ingredients are fully incorporated.
Stir in the chopped dill, if using. Season with salt and pepper to taste.
Preheat your oven to 375°F (190°C).
Brush a 9x13-inch baking dish with melted butter.
Place one sheet of phyllo dough in the dish and brush it with melted butter. Repeat this process, layering and buttering each sheet, until you have about 4-5 layers.
Spread a portion of the filling mixture evenly over the phyllo dough.
Continue layering phyllo sheets, brushing each sheet with melted butter, and adding more filling between layers. Repeat until all the filling is used, ending with a final layer of 4-5 phyllo sheets.
Cut the assembled banitsa into squares or diamonds with a sharp knife.
Bake in the preheated oven for 30-40 minutes, or until the banitsa is golden brown and crisp.
Allow the banitsa to cool slightly before serving. It can be enjoyed warm or at room temperature.
Enjoy your meal!