Wash the spinach, removing and discarding the thick stems. Dry the spinach thoroughly, and divide it among 4 large plates.
Wash the tomatoes and cut them in half through their stem ends.
In a saucepan, heat the olive oil over medium-high heat and add the garlic and halved tomatoes. Cook for 5 minutes, until the tomatoes soften and release some of their juices (but do not overcook, as the tomatoes should hold their shape).
Season with salt and freshly ground pepper. Spoon the warm tomatoes, garlic, and pan juices evenly over the spinach. Serve immediately.