Over a bowl, cut out grapefruit segments. Place segments in a separate bowl.
Once segments removed squeeze all the juice out of the grapefruit and add ½ Tbsp of sugar, and 1 Tbsp rice vinegar.
In blender add zest, juice, sugar, vinegar and a dash of cumin.
Blend ingredients and then slowly drizzle olive oil in. Start with ½ cup of olive oil, but adjust for taste.