1/2 teaspoon cayenne powder (more or less to taste)
1 pint half-and-half
1 cup sour cream, divided use
Garnish Sour cream, cilantro and tortilla strips
In a large saucepan over medium-high heat, melt butter; sauté onions until tender, about 5 minutes. Sprinkle in flour and garlic; cook, stirring constantly, for one minute.Slowly add half-and-half, whisking until mixture is thickened and creamy.Reduce heat to medium, and add diced tomatoes, diced tomatoes with green chiles, and seasonings (cilantro through cayenne); bring to a simmer, stirring frequently.Remove from heat, and carefully blend soup using an immersion blender, or puree in blender until smooth.Stir in 1/3 cup of sour cream, and use remaining sour cream to garnish each serving.