Tomato Pie-0-Mary Mac's in Atlanta Recipe - (4/5)

Ingredients

• 2 tablespoons olive oil
• 2 medium sweet onions (thinly sliced)
• salt and freshly ground black pepper
• 1 box of Ritz crackers
• 2 28 ounce cans diced tomatoes (undrained)
• 2 cups mayonnaise
• 1 1/2 cups grated extra sharp Cheddar cheese
• 1 cup grated Parmesan cheese
• 3 tablespoons chopped fresh basil
• Butter for greasing