Preheat your oven to 350°F (175°C).
In a skillet, melt 1 tablespoon of butter over medium heat. Add the chopped onion and cook until softened, about 5 minutes. Stir in the minced garlic and cook for an additional minute. Remove from heat and set aside.
In a large bowl, combine the cornmeal, grated cheese, baking powder, salt, black pepper, and ground cumin (if using).
In a separate bowl, whisk together the milk, melted butter, and eggs.
Add the wet ingredients to the dry ingredients and mix until well combined. Stir in the cooked onion and garlic mixture.
Grease a baking dish or casserole dish.
Pour the mixture into the prepared dish and spread it out evenly.
Bake in the preheated oven for 30-40 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Allow the Sopa Paraguaya to cool slightly before cutting into squares or serving.
Garnish with fresh parsley if desired.
Enjoy your meal!