Preheat the oven to 400°F and place the chopped asparagus, onions, and garlic on a large baking sheet.

Drizzle olive oil on top, and roast for 25 minutes, tossing halfway through.

While the vegetables are roasting, cook the bacon in a large skillet for 10 minutes or until the bacon is crispy.

Transfer the bacon onto a plate covered with paper towels, and let the oil soak up before cutting into small pieces.

Once the vegetables are tender, reserve a few asparagus spears for later, and transfer the rest into a blender with water and salt. Pulse until you get a thick, smooth mixture.

Pour the asparagus mixture into a large pot, and warm over medium heat for five minutes.

Ladle the soup into two bowls, drizzle the tahini on top, and garnish with reserved asparagus spears.

Sprinkle the bacon pieces on top and enjoy warm!