Preheat the oven to 320°F (160°C). Line a 12-inch loaf pan with parchment paper. In a food processor, blend the cottage cheese, Greek yogurt, eggs, vanilla, Monk fruit, cornstarch, and lemon zest (optional) until smooth. Pour the mixture into the prepared pan and top with the frozen berries.
Bake for 50–60 minutes, or until the center is set but still slightly jiggly. Baking time may vary depending on the type of pan you use.
Remove from the oven and let it cool at room temperature. Refrigerate until fully chilled; the flavor and texture are best when cold. Keep refrigerated.