Preheat your oven to 375°F (190°C). Lightly grease a 9-inch pie dish with butter or cooking spray.

Heat olive oil in a skillet over medium heat. Add the diced yellow onion and cook until softened, about 5-7 minutes. Add the minced garlic and cook for another minute until fragrant. Stir in the chopped fresh spinach and cook until wilted, about 2-3 minutes. Remove from heat and set aside to cool slightly. Squeeze out any excess liquid from the spinach mixture.

In a large mixing bowl, whisk the eggs until light and frothy. Add the cottage cheese, milk, all-purpose flour (or cornstarch), baking powder, salt, black pepper, and ground nutmeg. Whisk until well combined and relatively smooth.

Fold the cooled spinach and onion mixture and the shredded cheese into the egg and cottage cheese mixture. Mix gently until evenly distributed.

Pour the quiche mixture into the prepared 9-inch pie dish. Place the dish on a baking sheet to catch any potential drips.

Bake for 40-50 minutes, or until the center is set and a knife inserted into the middle comes out clean. The top should be golden brown.

Remove the quiche from the oven and let it rest for at least 10-15 minutes before slicing and serving. This allows it to set completely. Serve warm or at room temperature.