Step 1Put the chipotle puree in a blender and juice the orange into it. Add the salt.
Step 2Cut one of the orange halves in half again; and then cut that half in half to make an eighth of an orange. Cut away the pulp from the peel of that section, but leave the white pith. Dice the peel and pith as finely as possible and add to the blender. Grind chipotle, juice and orange in the blender to a coarse puree. Season to taste.
Step 3Put the shrimp in a plastic bag; add the puree and the onion. Seal tightly; refrigerate at least 1 hour.
Step 4Empty into a serving bowl and spear each shrimp with a toothpick.