1-Melt the butter in a skillet over medium-high heat and add the sliced onions in a single layer. Let them cook until they begin to brown, then lower the heat and stir only when needed to caramelize them to a dark color. Once done, set them aside to cool.

2-Mix the mayonnaise and creamy horseradish together to make a spread that adds a zesty touch. You can mash the roasted garlic cloves into this spread or keep them whole for added bursts of flavor on the sandwich.

3-Dress the arugula by tossing it with olive oil and white balsamic vinegar or lemon juice, and season with salt and pepper if you like. This step adds a fresh, crunchy element to balance the rich prime rib.

4-Assemble the sandwich by spreading the horseradish mayo on the bread slices, then layer on the dressed arugula, thinly sliced prime rib, and caramelized onions. For the best taste, serve the sandwiches cold to keep the meat tender and flavorful. more prime rib recipes can help if you want more ideas.

5-Enjoy your sandwiches right away for the freshest experience. This quick process, with just 5 minutes of prep and 15 minutes of cook time, makes 4 servings in under 20 minutes total.