Start by heating avocado oil in a large skillet over medium-high heat. Add diced onions and cook until soft and slightly golden. Then stir in garlic and ginger, cooking briefly until fragrant. This step builds the flavor foundation of the dish.
Add ground beef to the skillet and break it apart using a spatula. Cook until fully browned and no pink remains. Allow the meat to develop slight caramelization for deeper flavor. Drain excess fat if desired, though keeping some adds richness.
Stir in coconut aminos, gochujang, sesame oil, and black pepper. Let everything simmer for a few minutes so the sauce thickens slightly and coats the beef evenly. Taste and adjust seasoning if needed before removing from heat.
In a separate bowl, combine sliced cucumber with rice vinegar and sesame seeds. Toss gently to coat. Let it sit for a few minutes to absorb the tangy flavor. Serve alongside or on top of the beef.