Preheat the oven to 350 degrees. Press the pie crust into the bottom of a pie or tart pan and up the sides. Set aside.
In a skillet, cook the sausage, onion, and garlic breaking the sausage into small pieces as it cooks. Once cooked through, drain the excess liquid and place in the prepared pie pan.
In a mixing bowl, whisk together the egg, milk, and yogurt until smooth. Pour over the sausage. Arrange the tomatoes on top. Bake 35 to 40 minutes. Remove from oven and sprinkle basil over top. Let sit 20 minutes before slicing and serving.