Cut the corn from the cobs and set aside.
In a large heavy skillet heat the butter and oil. Sauté the onions and garlic for 2 minutes, stirring.
Add the jalapeño and tomatoes and cook, stirring for 3 minutes.
Stir in the corn and cook 4 to 5 minutes longer.
Add the seasonings.
Taste and correct the seasonings.
Stir in the cilantro just before serving.
Serves 6 to 8.