In the food processor, add the flour and salt, pulse to combine. Turn the processor on and add cubes of butter, a couple cubes at a time. Scrape sides as needed. Dough should look crumbly.
Add in the ice cold water until the dough comes together in a ball. You may need more or less water for this step. Once the dough comes together, wrap it up and refrigerate at least one hour, but the longer the better.
While refrigerating, slice up 1 large heirloom and 1 pint rainbow cherry tomatoes. Place face down on paper towel. With another paper towel, gently press into heirloom slices and let sit. After ~10 minutes remove paper towel. Sprinkle with salt, pepper, garlic powder, onion powder, and massage into the heirloom slices.
Preheat oven to 400°F.
Place parchment paper on pan and roll out crust into a rough circle
Leaving about 1 ½ - 2 inches on the border, spread herded goat cheese in the center. Optional - add layer of shredded mozzarella or shredded parmesan.
Lay your heirloom slices overlapping, and place your halved cherry tomatoes seed side up. Place them in any orientation - we went for a true rainbow.
Sprinkle with a pinch of salt, pepper, parsley, basil, and oregano. Follow up with a small drizzle of quality olive oil to just barely coat the tomatoes.
Fold the sides up (they don't have to be perfect) to tuck the baby tomatoes into their little tomato bed. Place in the oven on the bottom rack and bake for 15 minutes, rotate, and bake another 15 minutes. Remove tart.
Turn the oven up to broil (500°F) and shred a thin layer of parmesan over top of the tomatoes. Place back in the oven for 5-10 minutes, keeping an eye so the cheese doesn't burn.
This can be served warm out of the oven, or cold the next day with a summer mixed green salad.