Heat oil in a large skillet over medium-high heat. Saute onion until golden brown, about 5 minutes. Transfer onion and 1 tablespoon of the oil from the skillet to a food processor and puree until smooth. Reserve remaining oil in the skillet.
Place onion puree, beef, egg, yogurt, garlic paste, ginger paste, coriander, salt, and red pepper in a bowl. Mix by hand to combine. Form beef mixture into 4 to 5-inch-long kebabs using oiled hands. Arrange in a baking pan.
Saute cumin seeds in the reserved oil over medium-high heat until blackened, about 5 minutes. Stir in tomato sauce, and salt; cook until heated through, about 5 minutes more. Pour the sauce over the kebabs. Cover with aluminum foil.
Bake in the preheated oven until beef is no longer pink in the center, about 20 minutes. Uncover and turn on the broiler. Broil until brown, about 5 minutes more.