Preheat oven to 350. Remove peppers from jar and blot excess water with paper towels and chop.

In a bowl, soften cream cheese in microwave so it will be easier to stir. Add in the mayonnaise, onion, garlic, and Dijon. Stir to combine and then add in grated cheese and the diced peppers. Place in an 8x8-ish dish (a pie plate works great). At this point you can pop it in the fridge if you're going to cook it later and you can even prep it a couple of days ahead of time. Place in the oven and cook for 30-45 minutes. Baking time depends on the dish. It will start to bubble and brown on the outside edge, and you want it to be bubbly all the way through to the center. It will be nice and golden brown on top, especially around the edges (mine usually takes 40-45 minutes). Serve immediately.