Combine all ingredients except the shrimp and whole lemon in a 2-cup jar and screw the lid on tightly. Shake for 10 seconds. Let the dressing sit 15 minutes to rehydrate the dried herbs.
Place the shrimp in a large bowl. Pour enough dressing to cover but not drown them - you’ll use about a third of it. This part of the recipe is not exacting in any way. Stir to combine and let sit no more than 15 minutes.
Meanwhile, preheat your grill or grill pan to high; let it get really hot. Grill the shrimp until just cooked through, flipping once. Timing will vary depending on the size of your shrimp, but shrimp never take long to cook. You’re looking for the centers (where the vein was) to be opaque and they will curl a bit and turn pink. Also, they will feel very firm when you press them with tongs.
While you’re grilling the shrimp, place the lemon halves cut side down onto the grill and get them nice and charred.
Remove the shrimp to a platter and squeeze the charred lemon halves over. Serve immediately.