2) Remove from the heat and leave to sit to cool for 2 minutes. Pour into a blender and add the chipotle, tomato ketchup and salt. Blend for approximately 30 seconds.
3) Slice the remaining 1 1/2 red onions. Heat the oil in a large saute pan over a medium-high heat. Add the onions and saute until golden brown.
4) Stir in the prawns and garlic salt and cook for 2 minutes. Pour the sauce over the prawns and simmer for 5 to 8 minutes. Transfer to a serving bowl and serve over Mexican rice, if desired.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network chefs have not tested this recipe, in the proportions indicated, and therefore we cannot make any representation as to the results.