Before starting, remove 2 tbsp butter (dbl for 4 ppl) from the fridge and set aside to come up to room temperature. Preheat the oven to 450˚F. Wash and dry all produce. Peel, then cut onion into 1/8-inch slices. Heat a medium pot over medium heat. When hot, add 1/2 tbsp butter (dbl for 4 ppl), then onions. (NOTE: Do not use the softened butter in this step or step 3; save it for step 4.) Cook, stirring occasionally, until golden-brown, 5-7 min. Reduce heat to medium-low, then add half the balsamic glaze and season with salt and pepper. Cook, stirring occasionally, until onions are dark golden-brown, 2-3 min. Remove the pot from heat.

Meanwhile, halve rolls. Core, then cut apple into 1/4-inch slices. Cut tomato into 1/2-inch pieces. Add remaining balsamic glaze and 1/2 tbsp oil (dbl for 4 ppl) to a large bowl. Season with salt and pepper, then whisk to combine. Cut brie into 1/4-inch slices.

Heat a large non-stick pan over medium-high heat. When hot, add 1/2 tbsp butter (dbl for 4 ppl), then swirl the pan until melted. Add apples, then sprinkle with 1/4 tsp sugar (dbl for 4 ppl). Cook, stirring occasionally, until warmed through, 1-2 min. Transfer apples to a plate to cool.

Meanwhile, spread 2 tbsp softened butter on cut sides of rolls. Arrange bottom rolls on a parchment-lined baking sheet, cut-side up. Set top rolls aside. Toast bottom rolls in the top of the oven until warmed, 3-5 min. (TIP: Keep an eye on rolls so they don't burn!)

Spread Dijon on toasted bottom rolls. Top with apples, caramelized onions, then brie. Arrange assembled bottom rolls and buttered top rolls on the same parchment-lined baking sheet, cut-side up. Toast in the top of the oven until brie is slightly melted, 3-5 min. (TIP: If you want meltier brie, continue toasting until desired doneness.)

Meanwhile, add spinach and tomatoes to the bowl with vinaigrette. Toss to combine. When brie is slightly melted, spoon fig spread over top rolls, then close melts. Halve crosswise, if desired. Divide melts and salad between plates. Sprinkle salad topping mix over salad.