To start, preheat the oven to 425 degrees F.
Wash and trim the hard ends off the asparagus (keep the "flowering" head side on). On a baking sheet, toss with the olive oil, lemon juice, lemon zest, salt, pepper, and red pepper flakes. Mix well.
Roast asparagus for 15 minutes. Then, take out the tray and stir the asparagus around. Put asparagus back in the oven for another 10-15 minutes or so, or until slightly browned around the edges and fork-tender.
While asparagus is roasting, prepare the caesar dressing. Add all dressing ingredients to a food processor or blender and blend on high until incorporated. Taste, and adjust seasonings to your liking. See blog post for troubleshooting tips.
Make the sourdough croutons by tearing or cutting the sourdough bread into 3/4 - 1 inch pieces. Add to a pan and drizzle pieces with olive oil, then sprinkle with pinch of salt and black pepper. Over medium low heat, cook croutons until they've started to brown, mixing often to prevent burning.
Prepare your lettuce by washing, drying, and cutting up romaine and radicchio (if using). Cut into rough chunks or bite-sized pieces, whatever you prefer.
Assemble the salad - on the bed of lettuce, layer on the asparagus and croutons. Drizzle everything with the caesar dressing.
Enjoy!