In a large cast-iron skillet, heat 1 tbsp oil over medium-high heat. Season the salmon with ½ tsp salt.
Add salmon skin side up. Let sit until golden (about 4 mins.)
Flip the salmon & cook until golden on the other side (about 2 mins.) Remove from heat to a plate.
Reduce heat to medium & add remaining oil & onion to skillet.
Cook & stir occasionally until softened (about 2 mins.) Add garlic & ginger & cook until fragrant (about 1 min.)
Stir in coconut milk & bring to a simmer. Cook & stir occasionally until thickened (about 5 mins.) Add in lime juice & ½ tsp salt.
Remove from heat & return the salmon to your pan. Garnish with basil & enjoy!