In a large (12-inch) saute pan over medium heat, heat the oil and butter. Add the diced bell pepper and onion and cook until the bell pepper has softened and the onion is beginning to brown lightly, about 8 minutes. Add the cumin and salt and pepper to taste and cook, stirring, for 1 minute. Add the corn and cook for 3 to 4 minutes until the corn is heated through. Remove from heat, mix in the cilantro and serve.