Heat oil in a large heavy saute pan or iron skillet over high heat until almost smoking hot.
Coat the salmon fillets well on both sides with the blackening spice and place gently in the hot pan. Sear on the first side for about 2 minutes and then flip fish over. Add the black beans to 1 corner of the pan and throw in the fresh spinach and butter right on top of everything and cook it all for about 2 minutes more.
To serve, take the spinach off the top and place it on the bottom of a plate. Then arrange the salmon and black beans around it. Garnish with a dollop of sour cream, if desired.
Mix all the blackening spice ingredients well and store in a sealed container or spice canister. Keep extra as a versatile spice in your kitchen.