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.