Boil the pasta for 12 minutes then add the cut asparagus to the boiling water. Cook for an additional 2 to 3 minutes and then drain pasta and asparagus in a strainer and run under cold water until pasta and asparagus have cooled. Drain completely and place in a large bowl.
Add in the tomato and onion and toss to coat.
Meanwhile whisk together all the ingredients for the dressing and pour over pasta. Stir to coat. Serve chilled. Enjoy!