In a large pot of salted boiling water, add the fettuccine or spaghetti. Cook according to package instructions until al dente. Reserve about 1/2 cup of pasta water before draining, then set the pasta aside.
Season the sliced flank steak with salt, pepper, and red pepper flakes. In a large skillet, heat 1 tablespoon of olive oil over medium-high heat. Add the steak in a single layer and sear for about 2-3 minutes on each side, until browned and cooked to your preferred doneness. Remove from the skillet and let it rest.
In the same skillet, add the remaining tablespoon of olive oil. Toss in the minced garlic, sliced bell pepper, and zucchini. Sauté for about 4-5 minutes, or until the vegetables are tender but still vibrant.
In a small bowl, combine honey, soy sauce, rice vinegar, and additional red pepper flakes (if desired). Pour this mixture over the sautéed vegetables in the skillet, stirring to coat well.
Slice the rested steak into bite-sized pieces. Add the drained pasta and steak to the skillet with vegetables and sauce. Toss everything together, adding reserved pasta water a little at a time if necessary to loosen the sauce and help distribute flavors evenly.
Taste and adjust seasoning, sprinkle with additional salt or pepper as needed. Serve the pasta hot, garnished with fresh basil leaves and grated Parmesan cheese, if using.
Notes
Adjust red pepper flakes according to spice preference.