Preheat oven to 425°.
To prepare pork, combine first 5 ingredients, and rub over pork. Place pork on a jelly roll pan. Bake at 425° for 25 minutes or until a thermometer registers 160° (slightly pink). Let the pork stand 5 minutes before slicing.
To prepare salsa, discard husks and stems from tomatillos. Finely chop tomatillos; place in a medium bowl. Add avocado and remaining ingredients; toss well.