Preheat the oven to 350 degrees F. Cut the scones in half and spread the cut side with the butter. Set the scones on a baking sheet. Top each half scone with spinach. Top the spinach with two slices of tomato. Season with salt and pepper. Heat in the oven 10 to 12 minutes, or until the spinach is slightly wilted.
While the scones heat, bring a large pot of water to a gentle simmer and add the vinegar. Poach eggs to desired doneness. Set two half scones on each of 4 plates. Top each with an egg and serve.