Bring a medium pot of water to a boil and cook the soba noodles for 4 to 5 minutes until al dente, then drain and rinse with cold water to prevent sticking.
Heat a large skillet over medium-high heat and add the ground beef, breaking it into small crumbles with a wooden spoon.
Season the beef with sea salt and black pepper, browning it thoroughly until no pink remains.
Push the beef to one side of the skillet and add the sesame oil, sliced bell peppers, and onions to the empty side.
Sauté the vegetables for 3 to 4 minutes until they are tender-crisp and the onions are slightly translucent.
Stir in the minced garlic and grated fresh ginger, cooking for 30 seconds until the mixture is highly aromatic.
Add the cooked soba noodles and tamari to the skillet, tossing everything together for 1 minute to ensure the noodles are heated through and coated in sauce.
Remove from heat and garnish with freshly chopped green onions before serving.