Bring a large pot of salted water to a boil and add spaghetti. Cook according to package directions (usually around 9-10 minutes) until al dente. Don't overcook it or you'll end up with mushy noodles that won't hold the sauce properly. Reserve 1/2 cup pasta water before draining—you'll need this later to loosen everything up.

While the pasta cooks, heat olive oil in a large skillet over medium heat. Add chicken strips and cook for about 5-6 minutes until they're mostly cooked through and starting to get golden at the edges. Season with a pinch of salt and pepper as you go, tasting to make sure it's seasoned enough.

Add minced garlic and red pepper flakes to the skillet with the chicken. Stir constantly for 30 seconds to 1 minute until you can smell the garlic—don't let it burn or it gets bitter and kinda ruins everything. The kitchen should smell amazing at this point, honestly.

Add the butter and lemon juice to the skillet once the garlic's fragrant. Let the butter melt completely and swirl everything together, then immediately add lemon zest. The juice and zest together create that bright spring vibe, so both matter here (don't skip the zest thinking juice alone is enough).

Toss in the drained spaghetti and toss everything constantly for 1-2 minutes. Add 1/4 cup of that reserved pasta water slowly while tossing—the starch in the water helps create a silky sauce that coats each noodle. It'll look kinda thin at first but thickens up fast once everything combines.

Remove the skillet from heat and stir in fresh parsley and Parmesan cheese. Taste and adjust salt and pepper as needed—mine always needs a tiny bit more salt than I expect. If it looks too thick, add a splash more pasta water (just 2-3 tablespoons at a time) until you get that creamy consistency you're after.

Divide between two bowls or plates and serve immediately while everything's hot and saucy. Crack a little extra black pepper on top if you want, and maybe a few more Parmesan shreds. I always eat mine within 5 minutes because the sauce stays perfect and silky when you dig in right away.