Slice tomatoes and lay sliced on plates. Sprinkle lightly with salt and let sit at least 10-20 minutes, and up to 30 minutes.
Melt butter in small skillet over medium-high heat. Add onion and garlic and saute' until onions are soft (about 8 minutes). Transfer to a medium-sized bowl.
Add cheese, eggs, herbs, and pepper to bowl. Stir to combine.
Drain water off of plates with tomatoes, With a paper towel, Gently blot tomatoes to soak up excess moisture.
Arrange tomatoes in a single layer on a greased pie pan. Top with about ¼ cup of the cheese mixture. Repeat until all ingredients have been used, finishing with a layer of tomatoes. Top this layer with a sprinkle of mozzarella cheese.
Bake at 375 degrees for 30-40 minutes, or until edges are lightly browned.
Allow to sit 5-7 minutes before serving.
Be sure to follow all the tips for salting and draining the tomatoes. This is key to keep your crustless tomato pie from being soggy.