Gently bend each asparagus spear until it breaks naturally (Usually 1-2 inches in from the bottom). Discard the woody end, then slice remaining spear into thirds. Set aside.
In a saute pan over medium heat, add butter. Once melted, add onions. Cook for 3-4 minutes - onions will begin to brown and turn translucent. Add minced garlic, red pepper flakes, and pepper. Stir to combine. Cook for 1 more minute.
Add bow tie pasta and vegetable broth to pan. Scrape to deglaze pan if needed. Bring to a boil, cover, and reduce heat to low. Simmer for 9 minutes (or consult your pasta package directions and cook to al dente, minus 4 minutes).
Uncover, add asparagus, and stir to combine. Cover and simmer for an additional 4 minutes (for very thin asparagus, reduce time to 3 minutes. For very thick asparagus, increase time to 5 minutes).
Uncover pan. Most of liquid should be absorbed. Add heavy cream and parmesan cheese, stirring to combine. Cook for 2 minutes to heat through and allow cheese to melt.
Remove from heat and allow to set for 5 minutes before serving (sauce will continue to thicken in this time).