Bring a large pot of salted water to a boil. Cook, stirring once or twice, for 1 minute less than the suggested cooking time on the package. The pasta will finish cooking in the sauce. Reserve ½ cup of the pasta cooking water.
Using a damp paper towel, brush off dirt from the mushrooms. Cut away and discard any hard stems. Chop into ¼-inch slices or, if the mushrooms are larger, like portobello, cut into ¼-inch cubes.
Use a microplane to zest the lemon finely. You need 1 tablespoon.
Heat the olive oil in a large, wide skillet over medium heat. Add the mushrooms and spread into one layer. Then cook, without moving, until browned on one side, 3 to 5 minutes.
Stir, and cook another 3 to 5 minutes, or until mostly golden brown on all sides. Stir in butter, garlic, thyme, mushroom powder, lemon zest, and ¼ teaspoon salt.
Turn the heat to low and add the drained pasta, ¼ cup parmesan, and ¼ cup of the reserved pasta water. Use tongs to toss the pasta, cheese, and mushrooms around the pan for one minute.
If the pasta looks dry, add a splash more pasta water. I usually use the full ½ cup of pasta water.
Taste and adjust the seasoning. Squeeze over half a lemon. Serve with parmesan and fresh ground black pepper on top.
