SAUTE: Heat oil in skillet to medium high. Add onions and saute for 5 minutes, stirring occasionally. Add garlic and all seasonings. Stir and saute until fragrant for anther 2 minutes.
ADD LIQUIDS AND SIMMER: Add tomatoes with juices, coconut milk and cilantro. (If using whole tomatoes, crush by hand). Bring to boil, then lower to medium and simmer, uncovered for 12-15 minutes until slightly thickened. Add spinach if using and stir until wilted, one minute. [NOTE: if only serving salmon for 2, save half the sauce for another use.]
POACH SALMON: Add salmon and immerse in sauce. Cover skillet and simmer on medium low for 6-8 minutes, depending on thickness of salmon. Serve in bowls over rice, noodles or topped with homemade garlic croutons.
Nutrition values include a double portion of sauce, half of which can be used another time e.g. on pasta, rice, chicken, etc.