Steps
1. Heat the olive oil in a large skillet over medium-high heat.
2. Add the onions and garlic and cook until the onions are soft and lightly golden brown, about 10 minutes.
3. Add the tomatoes, red pepper flakes, cumin and salt and continue to cook for about 5 minutes, stirring frequently.
4. Add the fresh lime juice, reduce the heat to low and simmer for 2 minutes.
5. Remove from heat and set aside.
6. Heat the corn tortilla in a large skillet over medium-high heat until lightly golden, about 1 minute.
7. Add the caramelized onion mixture to the tortilla, top with cheese (optional), fold and enjoy.