Heat canola oil in a large saucepan over medium heat.

Add chopped onion and cook until softened, about 2-3 minutes.

Stir in chili powder and cumin and cook for 1 minute.

Add drained and rinsed black beans, water, salsa, and salt.

Bring the mixture to a boil.

Reduce heat and simmer for 10 minutes.

Remove from heat and stir in lime juice.

Transfer half of the soup to a blender and puree until smooth.

Stir the pureed soup back into the saucepan.

Heat through.

Serve garnished with reduced-fat sour cream and chopped fresh cilantro.