Before starting, preheat the oven to 450°F. Wash and dry all produce. Heat Guide for Step 5 (dbl for 4 ppl): 1/8 tsp mild, 1/4 tsp medium and 1/2 tsp spicy! Core, then cut pepper into 1/4-inch pieces. Zest, then juice half the lemon (whole lemon for 4 ppl). Cut any remaining lemon into wedges. Add mayo, lemon juice, lemon zest and half the garlic salt to a large bowl. Season with pepper, then stir to combine. Add half the peppers, then toss to coat.

Pat chicken dry with paper towels. Carefully slice into the centre of each chicken breast, lengthwise and parallel to the cutting board, leaving 1/2-inch intact on the other end. Open up chicken like a book. Season both sides with remaining garlic salt and pepper.

Heat a large non-stick pan over medium-high heat. When hot, add 1/2 tbsp oil (dbl for 4 ppl), then chicken. Pan-sear until golden-brown, 1-2 min per side. Remove the pan from heat. Transfer chicken to a parchment-lined baking sheet. Spoon marinara sauce over each piece of chicken. Top with remaining peppers, then sprinkle with cheese. Roast in the middle of the oven until chicken is cooked through, 10-12 min.**

Meanwhile, add spinach to the large bowl with dressing and peppers. Toss to combine.

Divide chicken and salad between plates. Sprinkle 1/8 tsp chili flakes over chicken. (NOTE: Reference heat guide.) Squeeze a lemon wedge over top, if desired.