Before starting, preheat the oven to 450°F. Wash and dry all produce. Peel, then cut onion into 1-inch pieces.Trim ends off broccolini, then halve any larger stalks lengthwise. Leave thinner stalks whole.Add broccolini and 1/2 tbsp (1 tbsp) oil to a medium bowl. Season with salt and pepper.Zest, then juice half the lemon. Cut remaining lemon into wedges. Add pesto, mayo and lemon zest to a small bowl, then stir to combine. (NOTE: This is your pesto mayo.)Reserve half the pesto mayo in another small bowl. Set aside.

Add onions, squash and 1 tbsp (2 tbsp) oil to a parchment-lined baking sheet. Season with 1/2 tsp (1 tsp) garlic salt and pepper, then toss to combine. Roast veggies in the middle of the oven, 10-11 min.Flip veggies, then add broccolini to the other side of the baking sheet. Return to the middle of the oven. Continue roasting until all veggies are tender, 10-11 min.

Meanwhile, heat a medium non-stick pan over medium-high heat. Add 2 tsp (4 tsp) oil, then panko. Toast, stirring often, until golden-brown, 2-3 min. Transfer toasted panko to a shallow dish.Season with salt and pepper, then toss to combine. Set aside.

Pat sea bass dry with paper towels. Season with 1/4 tsp (1/2 tsp) garlic salt and pepper. Arrange on an unlined baking sheet. Spread pesto mayo from one of the small bowls over tops of sea bass. Sprinkle with toasted panko, pressing gently to adhere. Roast in the top of the oven until sea bass is cooked through, 8-11 min.\*\*

Add 1 tsp (2 tsp) lemon juice to the other small bowl with reserved pesto mayo. Whisk to combine. Set aside.

Divide roasted veggies and panko-topped sea bass between plates. Drizzle veggies with lemony pesto drizzle. Squeeze a lemon wedge over top, if desired.