Brown the ground beef in a large pot over medium heat, breaking it apart with a spoon as it cooks. Drain any excess fat once the beef is fully browned.

Add the diced onion, minced garlic, and grated ginger to the pot. Cook for 3 to 4 minutes until the onion softens.

Stir in the Thai red curry paste and cook for 1 minute to release its aroma.

Pour in the coconut milk and beef broth. Add the sliced red bell pepper, fish sauce, and brown sugar. Bring the mixture to a simmer and cook for 10 minutes.

While the stew simmers, cook the rice noodles in a separate medium pot according to the package directions. Drain them in a colander.

Stir the lime juice into the stew. Divide the drained rice noodles among four bowls and ladle the stew over the top. Finish with chopped cilantro and peanuts if using.