Coming back to add some recipes, I realized you need toddler-friendly things.
Here are a few ideas that worked well for my nephews (though they never carried any of this for lunch, that was usually a bagel-cream cheese or pita-hummus, plus fruits and veggies 
).
Cuban black beans & rice - mildly flavored but delicious.
Khichdi - this is endlessly customizable, as you can change the type of bean, the level of seasoning, the texture (from soft risotto to more distinct grains), and vegetable add-ins. Here’s a simple version, here’s a more complex one.
Milk-braised beans - very mild but flavorful, though you might want to lighten up on the herbs for the kid.
Mujadara - again might need to lighten up on the onions for the kid, but it’s very tasty.
