Preheat your oven to 450°F (230°C). Cut the red peppers in half, remove the seeds and stems, and place them cut-side down on a baking sheet lined with parchment paper. Roast for about 20-25 minutes, or until the skins are blistered and the peppers are tender. Once done, remove them from the oven and let them cool slightly. After cooling, peel off the charred skins.
In a skillet, melt the butter over medium heat. Add the diced onions and sauté until they are translucent and fragrant, about 5-7 minutes. Add the minced garlic and continue to cook for an additional minute until the garlic is soft and aromatic. Remove from heat and let it cool.
In a mixing bowl or a food processor, combine the roasted red peppers, sautéed onions and garlic, cream cheese, and mayonnaise. Blend until smooth and creamy. Taste and add salt and pepper as desired. If you prefer a thinner dip, you can add a splash of water or extra mayonnaise to reach your desired consistency.
Transfer the dip to a serving bowl and refrigerate for at least 30 minutes to allow the flavors to meld together. Serve chilled or at room temperature with vegetables, pita chips, or crackers. Enjoy your Easy Roasted Red Pepper Dip!