Peel and cut satoimo into bite-sized pieces. Rub with a pinch of salt to remove slime, rinse, and drain. Place in a microwave-safe container, cover loosely with plastic wrap, and microwave at 600W for 6 minutes until tender.

Cut tofu into bite-sized pieces. Place on a paper towel in a microwave-safe container, wrap, and microwave at 600W for 2 minutes to remove excess water.

Finely mince the onion.

Combine all meat sauce ingredients in a microwave-safe container, mix, cover loosely with plastic wrap, and microwave at 600W for 2 minutes. Stir, cover again, and microwave for another 2 minutes.