Asparagus and Red Pepper with Balsamic Vinegar

• 1 tablespoon butter
• 1 tablespoon olive oil
• 1/2 bunch fresh asparagus, trimmed
• 1 red onion, sliced
• 1 red bell pepper, sliced
• salt to taste
• 1 tablespoon balsamic vinegar
• 1/4 cup Parmesan cheese
• 1 tablespoon sesame seeds (optional)
• 1 tablespoon toasted pine nuts (optional)

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Melt the butter with the olive oil in a large skillet over medium heat; add the asparagus and red onion in the mixture, season with salt, and cook until the onion begins to soften, about 5 minutes. Stir the red bell pepper into the mixture and continue cooking until the onions begin to caramelize, another 5 minutes. Remove from heat and add the vinegar, Parmesan cheese, sesame seeds, and pine nuts; toss to combine.