For the pico de gallo, combine the tomatoes, onion, cilantro, serrano chili pepper, olive oil and lime juice in a small bowl. Season with salt and pepper. Reserve.
Slice the avocados in half and remove the pits. (Optional: You can scoop a little bit of the avocado out, if the pit was small, to make more room for filling.)
Lightly brush the cut side of the avocados with some olive oil or spray them with a cooking spray.
Place the avocados, cut side down, on the preheated grill. Grill for 5 minutes or until you see some nice grill marks.
Remove from grill. Spoon some pico de gallo into the center of each avocado half.
Sprinkle with some sea salt flakes. Serve immediately!
Notes
If you scooped out some avocado, just toss it in a small bowl with some lemon juice to prevent it from browning quickly and then refrigerate it. Consume within the next couple of days.
Leave out the serrano chili pepper if you have a low heat tolerance.