In a large bowl, combine the vinegar, lime juice and salt and set aside.
Halve your tomatoes or cut in thirds if your tomatoes are very large. You want roughly ½" thick tomato slices. Add the tomatoes to your marinade bowl and mix to coat.
Heat your grill to high heat and place the tomatoes in a single layer, basting the tops with the chimichurri sauce. Cook for 3-5 minutes, or until grill marks form. Then flip and baste the other side with more chimichurri and cook for an additional 3-5 minutes. Do not overcook or the tomatoes will get too soft.
Notes
Use tomatoes that are firm (but ripe). Softer, overly ripe tomatoes will not hold up well on the grill.Do not cut your tomato slices too thin, or they won't hold up on the grill.Make sure not to overcook your tomatoes, or they will get too soft.