Masala Omelet Sandwich

Name: Masala Omelet Sandwich
Ingredients: 2 tablespoons milk; 1 tablespoon chopped fresh cilantro; Kosher salt and freshly cracked black peppercorns; 1/4 teaspoon garam masala; 1/4 teaspoon turmeric powder; 1/8 teaspoon red chile powder; 3 large eggs; 1 tablespoon salted butter; 1/2 teaspoon cumin seeds; 2 tablespoons finely chopped red onion; 1 tablespoon finely chopped tomatoes; 1/2 teaspoon finely chopped green chile peppers; 1 teaspoon finely chopped fresh ginger; 2 slices sourdough bread; 1/4 cup grated processed cheese (such as Amul) or white cheddar cheese; Hot and sweet ketchup (such as Maggi), for serving