Wash tomatoes – core tomatoes, then slice into 1/4 inch slices. Arrange half of the slices in a large and shallow casserole dish. Sprinkle half the sugar, salt and pepper on slices. Arrange remainder slices, then sprinkle with rest of sugar, salt and pepper. Drizzle vinegar over tomatoes. Cover and refrigerate for 1 1/2 – 2 hours before serving.