Season the portobello cap with salt and pepper; grill for about 3 minutes on each side or until heated through. Set aside.
Sauté garlic in olive oil until fragrant, about 1 minute. Be careful not to burn the garlic. Deglaze the pan with white wine; cook until reduced by half. Add sun-dried tomato pesto and butter; stir to fully incorporate. Remove from heat.
In a separate pan, wilt spinach in a little oil; season with salt and pepper.
Add pasta to the pesto sauce mixture; use tongs to combine. Place pasta in a serving bowl; top with spinach. Slice the portobello cap into 4 slices; fan the slices over the top of the pasta. Garnish with Parmesan cheese.
Servings: 1