In a mixing bowl, combine the egg, egg whites, water, salt and pepper and whisk together until thoroughly blended and beaten.

Bring a medium skillet over medium-high heat and add the butter. Make sure the butter coats the bottom of the pan as it melts. Once the butter is melted, add the egg mixture to the pan. Use a spatula to push the eggs from all around the edges into the center so that the set eggs are pushed into the middle and the egg liquid seeps back to the edges of the pan. When the edges are set and the center is getting there, drop small amounts of hummus in a line down the center of the omelet, then spread them a bit with the back of a spoon. Sprinkle most of the feta (I reserved a bit for the topping) over the hummus so that there is a straight line of filling down the middle.

Use a spatula to fold one side of the omelet over the center filling, then tilt the pan (folded side first) toward your plate and use the spatula to slide the omelet onto your plate and fold the other side of the omelet over the filling. Sprinkle the sliced basil and diced tomatoes over the top of the omelet along with any remaining feta and serve.