They want it on another plate
A different plate, a familiar bowl, or foods that are not touching can be the difference between eating and refusing.
The dish can change
Use the plate they accept. The food matters more than matching dishes.
The blue bowl, the divided plate, or a small ramekin are tools. They are not a regression.
Foods that touch
If they eat the banana only when it is off the avocado, put them side by side with a gap. Same meal, less conflict.
You can move the food once. Moving it five times becomes the game. Agree the bowl, then sit.
What stays the same
The familiar food is still there. The new food is still small. Only the dish changed.
At someone else’s house, bring the bowl if that is what makes eating possible. A familiar dish in a new room helps.
A sentence you can say
“We can use your bowl.”