Preheat oven to 425 degrees. In a food processor, place half the artichokes, the mayonnaise, cup Parmesan, lemon juice, and garlic. Process until smooth.
Add scallion and remaining artichokes; pulse once to combine. Transfer mixture to a 1-quart baking dish. Top with remaining tablespoon Parmesan.
Bake until golden and bubbling, 30 to 35 minutes. Garnish with scallion, and serve with crudites or pita chips.