Don Meijin at Bugis+ is more famous for its tendons (or tempura dons) but it also serves an assortment of donburis.
Their oyakodon is a tad pricey at $17. The portions though are generous even for a big eater like me. The katsu cutlet are thick, tender and juicy and the eggs cooked just right.
Its a good spot if you want something hearty, fuss-free and quick.