Cook the chopped bacon in a large pot over medium heat until crisp, about 5 minutes. Remove the bacon and set aside. Drain off all but 1 tablespoon of excess bacon grease.

To the pot, add the spicy Italian sausage and chopped yellow onion. Brown the sausage all over, breaking it up with a spoon, for about 5 to 8 minutes. Stir in the chopped celery, garlic, and a pinch of crushed red pepper flakes, cooking for 2 minutes.

Pour in the chicken broth, 1 cup of water, basil pesto, chopped sun-dried tomatoes, and lemon juice. Season with salt and pepper to taste. Bring the mixture to a boil over medium-high heat.

Stir in the fresh kale and cook for 5 minutes, or until wilted. Add the cheese tortellini and cook for an additional 2-3 minutes, or until tender. Stir in the heavy cream and grated parmesan cheese, then remove from the heat.

Stir in the reserved crisp bacon. Serve the soup immediately, topped with additional parmesan and fresh thyme, if desired.