In a blender, combine the brown sugar and hot water. Let sit to melt the brown sugar.
Juice the blood oranges and add to the blender. Add the tequila, orange liquer, lime juice, and ice to the blender.
Blend on high for 1 minute.
Brown Sugar Rim
On a flat plate combine the brown sugar, salt, and orange zest. On another plate, pour about 1 tablespoon lime juice or agave. Rim each glass with lime juice then dip into the brown sugar rim.
Fill each glass with frozen brown sugar blood orange margaritas and enjoy.