Heat a large skillet over high heat until hot. Add butter; spread to coat. Place salmon fillets flesh side down in skillet and sear for about 3 min or until browned. Using a slotted spatula, transfer to a plate, seared side up.
Add tomatoes to skillet and saute for 3 min or until browned and starting to pop; using spatula transfer to bowl.
Reduce heat to medium and let pan cool slightly. Add garlic to pan off the heat; saute for 15 sec, until fragrant.
Whisk flour into Cream; pour into skillet, stirring. Return skillet to the heat and bring to simmer, stirring constantly. Return salmon to pan, seared side up. Reduce heat to medium-low and simmer for 2 to 7 min (depending on thickness) or until salmon just flakes easily with a fork. Remove from heat.
Arrange lettuce on plates; top with tomatoes. Place salmon on top. Stir sauce in pan and drizzle over salads. Sprinkle with basil. Serve with lemon wedges to squeeze over top.
Before searing the salmon, be sure to let the pan get hot. Once you place the salmon in the pan, sear, without trying to lift it, until you can see the edges starting to brown; the salmon will fall apart if you try to lift it too soon.
Add 1 tbsp (15 mL) sun-dried tomato or basil pesto to sauce before adding salmon back to pan. Top salads with crisply-cooked strips of pancetta.