To make the gazpacho: Add the diced cucumbers, tomatillos, onions, and garlic to a mixing bowl. Pour in the olive oil, and sprinkle with the salt, and black pepper, to taste. Stir to combine and set aside to allow the flavors to blend. To make the scallops: Score the scallops with a small knife in a checkerboard pattern.
In a hot pan, add enough canola oil to line the bottom and sear the scallops on both sides until barely cooked through, about 30 seconds per side. Once cooked, they should just lose their translucent color. Serve the scallops by arranging the scallop shells on a platter. Place a dollop of the gazpacho onto each shell, and then top with a single seared scallop. Add a drizzle of olive oil and, lastly, a dusting of salt, and pepper.
Scoring will give the scallops a nice 'browned look' once they're seared.