Beef Crostini with Caramelized Onions and Horseradish Aioli

Ingredients:

• 1 lb roast beef or beef tenderloin
• Fresh basil leaves
• 2 yellow onions, thinly sliced
• 4 oz horseradish aioli
• Salt and pepper, to taste
• 4 tbsp olive oil
• 1 French baguette (12+ inches long)
• 8 oz Swiss cheese, sliced
  Instructions:

1. Preheat your oven to 375°F (190°C).
2. Heat 2 tablespoons of olive oil in a skillet over medium heat. Add the sliced onions and cook, stirring occasionally, until they are caramelized and golden brown, about 20-25 minutes. Season with salt and pepper to taste.
3. While the onions are caramelizing, slice the baguette into 1/2-inch thick slices. Place the slices on a baking sheet and brush both sides with the remaining olive oil.
4. Toast the baguette slices in the preheated oven for about 5-7 minutes, or until they are lightly golden and crispy.
5. Thinly slice the roast beef or beef tenderloin.
6. Assemble the crostini by spreading a layer of horseradish aioli on each toasted baguette slice.
7. Top each crostini with a slice of roast beef, a spoonful of caramelized onions, and a slice of Swiss cheese.
8. Return the assembled crostini to the oven and bake for another 5-7 minutes, or until the cheese is melted and bubbly.
9. Remove the crostini from the oven and garnish each one with a fresh basil leaf.
10. Serve the Beef Crostini with Caramelized Onions and Horseradish Aioli as a delicious appetizer or party snack.