In a large bowl, lightly beat eggs. Stir in pesto, salt, pepper, and 3/4 cup feta
In a 10-inch nonstick oven-safe skillet, heat oil over medium-high. Add spinach and stir to wilt. Add egg mixture and cook, stirring occasionally, 1 to 2 minutes. Thinly slice 2 of the tomatoes; arrange in a single layer on top and sprinkle with remaining feta
Bake until puffed and center is just set, 10 to 12 minutes. Let sit 5 minutes. Run a spatula around the edge and beneath before slicing into wedges. Serve remaining tomatoes, drizzled with olive oil and seasoned with fresh chives and sea salt
