Start your rice first since it takes the longest of any component here. Rinse it briefly under cold water, then cook it according to the package directions or in your rice cooker. While it simmers, you can move on to prepping your steak and vegetables.
Slice your ribeye as thin as you can manage, since thinner pieces sear faster and stay tender. Thinly slice your onion, shred your carrots, and chop your green onion while you're at it. Having everything prepped before you turn on the stove makes the cooking process move quickly.
Heat vegetable oil in a large skillet over medium heat until it shimmers slightly. Add the minced garlic and cook for about 30 seconds, just until it turns fragrant, being careful not to let it burn. Toss in the sliced onion and let it soften for a minute before adding the steak.
Add your thinly sliced ribeye to the pan and let it sear, stirring occasionally so it browns evenly. Cook until the onions turn translucent and the beef loses its pink color, which should take about five minutes total. If your pan feels crowded, cook the steak in two batches so it sears instead of steaming.
Pour the Korean BBQ sauce directly into the pan with the cooked steak and onions. Stir well so every piece gets coated evenly in that sticky, savory glaze. Let it cook for another minute so the sauce warms through and thickens slightly against the hot pan.
Remove the pan from heat once the sauce looks glossy and well distributed. Stir in your shredded carrots, sliced green onion, and sesame seeds right at the end so they stay fresh and crisp. This is also the point where you can taste and adjust with extra sauce if you want it saucier.
Scoop a generous bed of rice into each serving bowl as your base. Top it with the saucy steak mixture, making sure to spoon any extra sauce from the pan over the top. Serve immediately while everything is warm and the aromas are at their peak.