Cream of Tomato Soup

In a Dutch oven, over medium heat, saute onions in butter until translucent. Remove from the heat. Stir in the flour so that no lumps remain, then slowly whisk in the tomato juice. Return to the heat and add salt to taste. Cook until just boiling but turn off the heat before it boils. Let cool 10 minutes then slowly stir in milk. Serve immediately.