Place the shrimp in a bowl with baking soda, red pepper flakes, black pepper, and kosher salt.
Mix well and allow the shrimp to brine for 10 minutes.
Bring a large pot of salted water to a boil.
Cook the spaghetti until 1 minute less than al dente.
Reserve 2 cups of pasta water before draining.
Heat olive oil in a large skillet over medium heat.
Add the shrimp and sauté for about 3 minutes or until pink and firm.
Transfer the shrimp to a plate and tent loosely with foil.
In the same skillet, add the sliced garlic.
Cook for 2–3 minutes until lightly golden and fragrant.
If needed, add a little more olive oil.
Add 1/2 cup reserved pasta water to the skillet.
Stir in the butter until melted.
Add the drained spaghetti and toss to coat.
Cook for about 1 minute so the pasta absorbs the sauce.
Return the shrimp to the skillet.
Add parsley, lemon zest, and lemon juice.
Toss everything together until well combined.
Taste and adjust seasoning with salt, pepper, and additional red pepper flakes if desired.
Add more pasta water as needed to create a silky sauce.
Serve immediately while hot.