Dip rims of glasses in amaretto, then into sugar; set aside.
Combine all ingredients into the pitcher of the blender.
Add ice by small handfuls while <g class="gr_ gr_85 gr-alert gr_gramm gr_inline_cards gr_disable_anim_appear Grammar only-ins replaceWithoutSep" id="85" data-gr-id="85">blender</g> is running on med-high and continue adding until you reach your desired consistency. (Adding the ice in small batches makes for a smooth frozen margarita!)