Preheat the oven to 400 deg F

Spread the pumpkin seeds in a pie plate or on a small baking sheet and bake for 3 minutes, or until lightly toasted. Transfer to a plate and let cool.

Meanwhile, in a large bowl, combine 3 tablespoons of the olive oil with the lime juice, shallot and cilantro. Using a sharp knife, peel the grapefruit, removing all of the bitter white pith. Working over the bowl, cut in between the membranes to release the grapefruit sections into the bowl. Squeeze the juice from the membranes into the bowl; discard the membranes. Gently fold in the avocado and season with salt and pepper.

In a medium skillet, heat the remaining 2 tablespoons of olive oil until shimmering. Add the shrimp, season with salt and pepper and cook over moderate heat, tossing the shrimp until they are curled and pink, about 4 minutes.

Arrange the lettuce on a platter. Using a slotted spoon, lift the grapefruit and avocado from the citrus vinaigrette and gently spread over the lettuce
Add the shrimp to vinaigrette and toss to coat. Arrange the shrimp over the salad and drizzle the remaining citrus dressing on top. Scatter the toasted pumpkin seeds on top and serve right away