In a large saute pan over med heat cook onions and garlic until translucent, 3 to 5 minutes.
Stir in tomato puree and chipotle pepper and bring to a simmer over med heat. Continue to cook for 15 minutes, stirring occasionally to allow flavor to blend and sauce to reduce slightly. Lower heat if bottom of pan gets too hot so sauce does not burn.
Remove pan from heat and whisk in ream, then set aside. Makes about 1 1/4 cups of sauce.