Melt 2 tablespoons of butter in a large skillet over medium-low heat. Add thinly sliced yellow onions and cook for 30-40 minutes, stirring frequently until they become deeply golden and jammy in texture.

While the onions are caramelizing, set a fine-mesh strainer over a bowl and add the cottage cheese. Allow it to drain for at least 20 minutes, pressing gently with a spoon occasionally to remove excess liquid.

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

In a blender, combine the drained cottage cheese, 3 eggs, and 2 tablespoons of cornstarch. Blend until smooth and frothy, about 1-2 minutes.

Transfer the blended mixture to a large mixing bowl, stir in the caramelized onions, fresh thyme, salt, and pepper. Fold in ¾ cup of grated Gruyère cheese.

Pour the mixture into the prepared dish and top with the remaining ¼ cup of Gruyère cheese. Bake for 35-40 minutes, or until the edges are golden.

Once baked, remove from the oven and let it rest for 10-15 minutes before slicing.