Most supermarkets sell pickled tomatoes, but those can’t compare to these supereasy homemade ones. Slicing the tomatoes thinly allows them to really soak up the wonderfully tangy brine. Slideshow: More Pickle Recipes
Using a mandoline, very thinly slice the green tomatoes and white onion. Layer the slices in a heatproof 4-cup measuring cup. In a small saucepan, combine the water with the vinegar, garlic, peppercorns, salt and sugar and bring to a boil. Pour the hot brine over the tomatoes and onion and let cool to room temperature, about 1 hour. Cover and refrigerate for 1 hour, then drain and serve.
The drained pickles can be refrigerated for up to 2 weeks.