Fill a medium pot 3/4 of the way up with salted water; cover and heat to boiling on high. Wash and dry the fresh produce. Snap off and discard the tough, woody stem ends of the asparagus; cut into 1-inch pieces (keeping the pointed tips intact). Halve the lemon(s) crosswise; squeeze the juice into a bowl, straining out the seeds. Stack the prosciutto (removing the plastic lining between the slices), then thinly slice crosswise.

Add the pasta to the pot of boiling water. Cook, stirring occasionally, 8 to 10 minutes, or until al dente (still slightly firm to the bite). Turn off the heat. Reserving 1/2 cup of the pasta cooking water (or 1 cup for 4 servings), drain thoroughly.

Meanwhile, in a large nonstick pan, heat a drizzle of olive oil on medium-high until hot. Add the sliced prosciutto. Cook, stirring frequently and breaking apart any clumps, 4 to 5 minutes, or until crispy. Leaving any browned bits (or fond) in the pan, transfer to a paper towel-lined plate.

In the pan of reserved fond, heat a drizzle of olive oil on medium-high until hot. Add the asparagus pieces and as much of the red pepper flakes as you’d like, depending on how spicy you’d like the dish to be; season with salt and pepper. Cook, stirring occasionally, 4 to 5 minutes, or until lightly browned and softened.

To the pan, add the cooked pasta and half the reserved pasta cooking water (carefully, as the liquid may splatter). Cook, stirring constantly, 1 to 2 minutes, or until combined and the liquid has reduced in volume. Turn off the heat. Stir in the pesto, crème fraîche, and as much of the lemon juice as you'd like until combined and the pasta is coated (if necessary, gradually add the remaining cooking water to ensure the pasta is thoroughly coated). Taste, then season with salt and pepper if desired. Serve the finished pasta topped with the crispy prosciutto and parmesan. Enjoy!