When you need a convenient place to warm up single pots of food, the Nemco - 6310-1-240 - 240V Single Burner Hot Plate is just what you’ve been looking for. Use this single burner hot plate to safely cook a large variety of foods. The hot plate comes with a six-position temperature control and built in thermal protection to prevent fires and burns. The Nemco 240V Single Burner Hot Plate (6310-1-240) also features cast iron burners, brushed stainless steel and is ideal for small spaces. You’re going to love what it can do for you.
Yes, 220/240v are quite common in the US, especially for commercial grade equipment that needs more power. You can certainly browse many of our other Hotplate options here, and filter for 120v: https://www.etundra.com/restaurant-equipment/countertop-cooking-equipment/hot-plates/
Whether you're planning on doing the water bath method of canning or the pressure cooking method, you should be able to use this to can your tomatoes.
There are not temperatures marked on the dial. This is a Hi/Lo/Off dial.