Defrost a sheet of puff pastry. Clean your tomatoes, remove stems, and allow to dry. If using large green tomatoes, cut into large dice, or bite-sized wedges. Small or cherry sized tomatoes should be left whole to reduce moisture that can weight down the pastry.
Preheat oven to 420 F. For simple recipes like this one, the quality of ingredients matter. Buy your favorite thick-cut smoked bacon and cut it into squares by width. I use a breakfast coffee and black pepper cured bacon from my local butcher.
Render the fat and cook the bacon by heating it slowly over medium-low heat in an ungreased skillet, stirring occasionally. Take care not to burn the fat and protect yourself from splashing, continue to cook until completely crisp and brown. Drain the fat and reserve for another recipe. Let the bacon cool on paper towels to absorb remaining grease and finish crisping.
Cut cheese into large dice and toss with bacon and tomatoes. The mixture should be roughly equal but a few more tomatoes than bacon and cheese isn't a problem. Toss with salt and black pepper to taste.
On a sheet pan lined with parchment, unroll one puff pastry sheet and slice diagonally like a pinwheel. Make a heaping mound of filling in the center. Whisk egg and water to make an egg wash and paint onto every exposed part of pastry.
Fold and gently pinch the pastry into a free-form 'Galette' around the filling. If you have filling leftover add as much as you can into the center of the tart. Paint egg wash all over the exterior.
Bake for about 25-35 minutes, until dark brown on the sides and bottom. The center should be bubbling and beginning to brown. Let cool before slicing but serve warm.