While pasta is cooking, heat oil in a large skillet over medium-high heat. Add in onions, and cook until translucent, about 2-3 minutes.
Add in mushrooms and garlic, and cook, while starting occasionally for about 4-5 minutes. Season with thyme, salt, and pepper. Then add in tomatoes, and cook until tomatoes begin to tenderize about 3 more minutes.
Stir in the butter, lemon, and wine, and let cook, while stirring occasionally, until the wine reduces and the sauce begins to thicken.
Remove from heat, add in arugula, and gently toss until the arugula is wilted. Pour over drained pasta, and top each dish with 1 tbsp parmesan.