Cook the fettuccine in a large pot of salted boiling water until al dente, about 8-10 minutes. Reserve 1 cup of pasta water, drain, and set aside.

Heat vegetable oil in a large skillet over medium-high heat. Season the steak with salt and pepper, sear for 4-5 minutes on each side, then let rest for 5 minutes before slicing.

In the same skillet, reduce heat to medium and melt butter. Add garlic and sauté for 1 minute. Whisk in flour, then gradually add milk until thickened, about 3-4 minutes.

Stir in grated Parmesan cheese until melted and smooth. Taste and adjust seasoning with more salt and pepper if necessary.

Add halved cherry tomatoes and spinach to the sauce, cooking for 2-3 minutes until the spinach wilts and the tomatoes soften.

Toss the cooked fettuccine with the sauce and vegetables. Adjust consistency with reserved pasta water if needed.

Slice the rested steak and serve it on the fettuccine. Drizzle with balsamic glaze and garnish with parsley if desired.