Place Tomatoes, Onions, and Garlic in a bowl and pour oil into bowl. Gently toss vegetables to coat well with oil. Place vegetables on a sheet pan and arrange them evenly. Place sheet pan into a 500° oven until dark brown or just turning black then turn them so they are evenly browned. (don't worry if the vegetables begin to turn black, this time it is good to overcook the vegetables) Remove the sheet pan from the oven and place the vegetables in a food processor or a pan and blend with a hand blender fitted with a blade. The object is to puree the vegetables. As you puree the mixture add the Kosher salt, the stock, and the red curry paste. The soup should be fairly thick at this point so you may want to add more or less stock to suit your own preferences. Place the mixture in a pan and heat thoroughly. This will help to release the flavor of the curry. At this point the soup is ready to serve or you can make it more elegant by straining it through a chinois (fine mesh strainer) to remove the pulp. Serve hot with a lime wheel in the center and drizzle with lime juice.
You may also want to try garnishing with cilantro, basil, parsley, finely diced chiles, or come up with your own favorite garnish.