Heat a skillet to medium high.
Remove the sausage form the casing, break it apart and add it to the hot pan. As it is cooking break it up with a wooden spoon or spatula. Cook , stirring occasionally until the sausage begins to brown.
Remove from the pan and place on a plate lined with paper towels.
Slice the zucchini 1/4” thick.
Place the olive oil in a hot pan and add the zucchini slices. Brown them quickly on each side. You don’t want them to over cook and loose their shape or become mushy.
When done remove from pan and place on a dish lined with paper towel to absorb any excess moisture.
Slice the tomatoes 1/4” thick and blot on paper towel to remove any excess moisture or slice cherry or grape tomatoes lengthwise.
Preheat your oven to 425 degrees Fahrenheit.
On a lightly floured surface roll the dough into a 14” diameter circle and place it on a parchment lined baking sheet.
Pile the sausage in the middle of the crust leaving a 2 inch border all the way around.
Scatter the sliced zucchini over the sausage overlapping the slices.
Sprinkle the mozzarella cheese over the zucchini and then layer the sliced tomatoes over the cheese having them overlapping.
Fold the 2” border up over the filling leaving most of the filling exposed.
Beat the egg with a pinch of salt and brush it over the crust.
Sprinkle with some of the grated pecorino romano.
Place the galette in the freezer for 20 minutes , before baking, so the dough firms up and is nice and cold.
In the lower third of your oven, bake for 15 minutes. Reduce temp to 375° and bake for an additional 35-40 minutes or until golden brown.