In a large, nonstick skillet, heat olive oil over medium heat. Sauté onions for 4 minutes or until they start to turn translucent. While onions are cooking, cut the smoked sausage in half lengthwise, and then into pieces to create semi-circles. Add smoked sausages to the pan and brown lightly, 2 minutes.
Start cooking pasta in boiling water.
Rinse asparagus, snap woody ends off the bottom and discard. Cut remaining stalks into 1/2 inch pieces.
Stir in garlic and cook until fragrant, 1 minute. Add in the can of petite diced tomatoes, prepared asparagus, basil, salt, and pepper. Stir. Measure chicken broth into a liquid measuring cup and whisk in flour to dissolve. Pour chicken broth mixture into hot pan and bring to boil. As the sauce boils, it should thicken slightly. Reduce heat to low and stir in heavy cream. Taste sauce, adjust salt and pepper and continue to keep warm on low until pasta is finished cooking.
Drain pasta once it is cooked to your liking. Pour into sauce and toss to coat in sauce. Sauce may appear runny, but the more you stir the thicker it will become. It will come together :)