Boil a pot of water and cook rotini according to package directions. Drain, rinse, and set aside.
Slice the cherry tomatoes and olives in half and add to the pasta.
Peel and dice onion and garlic. Add to the pasta.
Mix mayo, olive oil, and vinegar in a bowl, whisking it together. Pour over the pasta and mix. Add Mrs. Dash seasoning and mix.
Clean the basil leaves and remove from the stem. Roll them into a log, then slice the log into small sections. This creates pretty ribbons of basil. Add to the pasta and mix it together.
Pour the mixed pasta into a bowl, cover, and refrigerate at least an hour to chill and marinade the flavors. Keep refrigerated and refrigerate any leftovers.