STOVETOP INSTRUCTIONS: Set a large pot of water on high heat and bring to a boil. Add a few pinches of salt. Then cook the pasta according to the package instructions. Usually 6-9 minutes for al dente pasta. Drain the pasta in a colander.
Meanwhile, set a large skillet over medium-high heat. Once hot, add the butter, garlic, and shrimp. Sprinkle with salt and pepper. Cook for 3-4 minutes, until the shrimp are pink. They should look like C's, not O's. O stands for overcooked.
Add the lime juice and half the cilantro. Stir well. Then toss in the cooked pasta, cream, and remaining cilantro. Stir for 1-2 minutes to coat the pasta and allow the sauce to thicken. Serve warm.
INSTANT POT INSTRUCTIONS: Place the pasta in the Instant Pot. Add the butter, garlic, 1/2 teaspoon salt, and 3 cups water. Cover and lock the lid into place.
Set the Instant Pot on "Pressure Cook High" for 4 minutes. Once it is finished cooking, turn the Instant Pot "Off", then press the button to "Quick Release" the steam, until the valve button drops.
Unlock the lid and stir in the lime juice, raw shrimp, cilantro, and cream. Set the Instant Pot on "Sauté" and cook for 3-4 minutes, toss and simmer until the shrimp are pink. Taste, then salt and pepper as needed. Serve warm.