Heat a large skillet over medium-high heat. Once hot, add the sesame oil and swirl to coat the pan.
Add the diced onion and sliced baby carrots. Cook for 5-6 minutes, stirring occasionally, until the vegetables are tender.
Add the chopped cauliflower and green bell pepper. Cook for another 3-4 minutes until the vegetables are tender-crisp.
Add the cooked rice, diced celery, and drained crushed pineapple. Stir to combine.
In a small bowl, mix together the soy sauce, maple syrup, ground ginger, black pepper, and garlic powder. Pour this sauce over the rice mixture and stir until everything is evenly coated.
Cook for an additional 2-3 minutes until the rice is heated through and the sauce has been absorbed.
Remove the skillet from the heat and sprinkle with cashews and red pepper flakes (if using). Serve immediately.