Add the beef to a skillet over medium-high heat and cook, stirring occasionally, until browned (about 8 minutes). If there's a lot of excess fat, spoon most of it out.
Meanwhile, boil a pot of water for the ramen noodles.
Take the skillet off the heat and stir in the sauce ingredients (peanut butter, hoisin sauce, sriracha sauce, soy sauce, ginger, and garlic).
Return the skillet to the heat and add in the red pepper (you will probably need to turn the heat down a bit). Continue cooking for a few more minutes, stirring often, until the pepper is tender-crisp.
The noodles only take about 3 minutes to cook, so I recommend adding the noodles to the boiling water just as you add the red pepper into the skillet.
Once the noodles are done, add 4 tablespoons (or so) of the cooking water into the skillet prior to draining them. Drain the noodles and add them to the skillet.
Toss well and season with extra salt & pepper if needed. Top with scallions if desired. Serve immediately.