Chicken curry. Tasty, nutritional, cheap, fast. Ingredients for one person, note that this scales up nicely:

• skinless, boneless, cubed chicken thigh (freeze skin/bones for homemade stock)
• seasoning of your choice (mine is curry powder, salt, minced garlic, hot pepper sauce, brown sugar)
• some veg oil
• half onion, grated
• 2tbsp tomato paste
• one potato, peeled, diced
• one carrot, peeled, sliced
• water or stock (cold is fine but boiling hot is preferable)
• 1 tsp (teaspoon) cornstarch
• [OPTIONAL] chives, parsley, sesame seeds, whatever garnish you'd like

1. Sprinkle seasoning over chicken thigh cubes. Sear them on high heat until brown outside, using the veg oil. Don't worry about the inside, they'll get cooked further.
2. Turn fire to low. Add onion. Let it cook a bit more, stirring often, until transparent. Add a bit of water as needed, you want it to melt down and thicken the sauce.
3. Add tomato paste, potato, carrot, and enough water/stock to cover everything. Test the seasoning, and correct it as necessary. (Note: potatoes absorb salt, so it'll taste now slightly saltier than the final dish. Take that into account.)
4. Wait until everything is cooked. The carrots and potatoes should take roughly the same time to cook, but if you're worried about one cooking faster, cut it in slightly larger chunks instead.
5. Use the cornstarch and a bit of water to make a slurry, then add it to the curry while mixing well. The sauce will be initially milky and runny, but as the cornstarch dissolves it'll become transparent and thicker.
6. [OPTIONAL] garnish!

Serve it alongside some flat bread, white rice, or polenta. I never did the nutrition maths for this recipe but it's three vegs, a source of protein, and the only fat there is from the meat and the veg oil that you used to brown it, so I'd say that it's healthy.

Variants: feel free to add cabbage or other vegs if you so desire. I don't recommend yucca for this one, it has a tendency to either dissolve into the sauce (some recipes exploit it... not this one). You can also swap the chicken thighs with breast, pork, or even some tougher beef cuts. Just take cooking times into account.