Heat large skillet or saucepan over medium heat. Once hot, add butter and let it melt and start to sizzle - about 1 minute.
Add minced garlic and jalapeño peppers and stir. Cook for 1-2 minutes, stirring frequently, then turn down heat.
Add flour 1 tablespoon at a time and whisk
Cook for 1 minute, then whisk in 16 oz yogurt, ½ cup at a time, until creamy.
Cook in skillet for 2 minutes, whisking frequently. Add nutritional yeast, salt, sweetener of choice, and hot sauce. (Optional: add to blender on high until creamy and smooth.)
Taste and adjust seasonings as needed, adding more nutritional yeast for extra cheesiness, salt for savoriness, or sweetener for flavor balance.
Simmer on low for 5 minutes, whisking or stirring often, to thicken.
Turn off heat and garnish with tomato and fresh cilantro (optional).
Store leftovers in a glass jar or container in the refrigerator up to 4-5 days. Reheat in the microwave or in a small saucepan over medium heat.