Combine jerk seasoning, lime or pineapple juice, 2 Tablespoons of the olive oil, and the honey in a large bowl. Whisk well to combine. Add shrimp and stir to coat. Let rest at room temperature for 15-20 minutes or in the refrigerator for up to 1 hour. (Don’t go longer!)
While the shrimp is marinating, bring a large pot of water to a rapid boil. Add a generous pinch of salt, then cook the pasta just to al dente. Scoop out a small amount of the pasta water, then drain the rest and set the pasta aside.
When ready to cook the shrimp, warm remaining 2 Tablespoons olive oil in a large skillet over medium-high heat. Pour in the shrimp and the marinade. Cook shrimp for 2-3 minutes per side, watching closely, just until they are opaque and cooked through. Remove shrimp to a plate and set aside.
Keep the skillet over medium-high heat and add the butter. When melted, add the sliced onion and cook for 3-4 minutes, until tender and lightly browned. Add pasta to the skillet and toss well to combine, adding a few Tablespoons of pasta water as desired to thin out the sauce.
Return shrimp to the pan, garnish with chopped fresh cilantro or parsley, and serve right away.