fiery
燉 centers on intense heat or a blazing quality: something fiery, glowing, or fiercely hot.
燉 combines 火 (fire) with 敦, which likely contributes the sound トン. The exact historical development is uncertain, but the structure suggests a phono-semantic compound where fire gives the meaning of blazing heat.
The left side is fire 火, and the right side 敦 looks like a sturdy pot being heated. Picture a pot over a fierce fire, glowing red-hot and fiery.
For トン, imagine a ton of blazing coals: ton -> トン, and the fire 火 makes them all fiercely hot.