Peel and dice the onion and garlic finely. Heat the oil over medium heat in a large pan. Add the onion and garlic and sauté for 2-3 minutes until translucent. Add the bulgur and fry for 1 minute. Pour in the vegetable stock, bring to a boil, then reduce heat to medium-low and simmer for 10 minutes.
While the bulgur is cooking, quarter the beefsteak tomatoes, remove the seeds, and cut into small cubes.
After 10 minutes, add the tomato cubes to the pan and cook for 5 minutes over medium heat.
Cut the feta cheese into small cubes. Add the feta to the pan, stir gently, and cook for 1-2 minutes until the feta begins to soften. Season to taste with salt and pepper.