First, make the pesto. Simply combine all the ingredients in the bowl of a food processor or blender. Blend till you achieve your desired consistency, I like my pesto to be quite smooth, some people like it coarser. Taste and adjust the lemon, salt and pepper. Set aside. At this stage, you can also stir in some toasted pine nuts or walnuts.
Bring a large pot of lightly salted water to a boil. Add the pasta and let it cook until it's soft but with a slight bite, about 10 minutes.
In the meantime, add the olive oil to a pan on medium high heat, along with the garlic. Stir briefly, then add the mushrooms with a light sprinkle of salt and pepper. Cook until the liquid has evaporated and the mushrooms have lightly browned around the edges. Transfer to a bowl, then add the tomatoes to the same bowl. Cook on high heat until they are blistered on the outside.
Now drain the cooked pasta (if you like a little bit of 'sauce', reserve 1/4 cup of the pasta water). Add it back to the pot, along with the pesto, mushrooms and tomatoes (plus the pasta water if desired). On low heat, stir everything together until the pesto has coated all of the pasta, and the pasta is warmed through.
Serve immediately, garnished with lots of parmesan or crumbled feta. Dig in! Leftovers can be stored in the fridge for 2 to 3 days. Happy cooking!