Cook the tortellini according to the package instructions. Strain, and run under cold water gently tossing until cool to the touch. Set aside.

In a small mixing bowl, add the sour cream, mayo, Ranch mix, and buttermilk. Whisk together until the sauce is smooth.

Transfer the tortellini to a serving bowl. Add the sauce, stirring until the pasta's evenly coated.

Add in the bacon & cheese, tossing until evenly combined.

Serve immediately, or cover & refrigerate a couple hours until the pasta salad's chilled through.