Heat a medium skillet over medium heat. Add 1 tablespoon butter and let it melt. Add the shrimp in a single layer and cook until pink and opaque, about 2 minutes per side. Transfer the shrimp to a plate and cover with a paper towel to keep warm.
In the same skillet over medium heat, add the 1/2 cup chopped onion. Cook, stirring occasionally, until the onion is tender, about 4 minutes.
Add the minced garlic and cook 1 minute. Add the grated ginger, 1/2 teaspoon sea salt, 1/2 teaspoon black pepper, and 1 tablespoon plus 1 teaspoon curry powder; stir to combine and cook about 30 seconds until fragrant.
In a small bowl, combine the remaining 1 tablespoon room-temperature butter with 1 tablespoon flour to form a smooth paste.
Pour in the 13 1/2 ounces coconut milk and add 1 teaspoon coconut palm sugar, stirring to combine. Bring the mixture to a boil, then reduce the heat to low.
Stir the butter-flour paste into the simmering coconut mixture and cook, stirring frequently, until the sauce starts to thicken, about 5 minutes.
Add the cooked shrimp back to the skillet and cook just until heated through, about 15 seconds.
Remove the skillet from the heat. Stir in 1 tablespoon lime juice and 1/2 cup chopped fresh cilantro.
Serve immediately (optionally over brown rice).