Preheat oven to 375 degrees F (190 degrees C). Grease muffin cups or line with paper muffin liners.
In a large bowl, combine flour, baking powder, baking soda, salt, basil, oregano and sugar into large bowl; stir until well blended. Mix in tomatoes, 1.5 cups of cheese and onions. In another bowl beat egg, whisk in buttermilk and stir until combined. Spoon batter into muffin tins until half full. Sprinkle remaining 1 cup cheese on top of muffins.
Bake in preheated oven for 15 to 20 minutes, until a toothpick inserted into center of the muffin comes out clean.
