Using a sharp paring knife, carefully cut away the peels from the oranges and grapefruit, reserving one half of an orange for the dressing. Cut into 1/2 inch slices and then in quarters, remove any thick pith.
In a small bowl, combine all dressing ingredients and whisk to combine.
Assemble salad in a large bowl with lettuce and orange and grapefruit, toss with the dressing. Add hazelnuts.