Remove the hard core of the cabbage head. Using the steamer insert, steam it core down with 2 cups of water. This should take about 20 minutes.

Add the chopped onions and butter to the Instant Pot. Use the Saute function on Low to melt the butter. It heats up quickly so turn the heat off (Cancel) to avoid browning.

Set the Instant Pot to Manual on High Pressure for 10 minutes. Do a quick release.

Remove the cooked onions and drain in a sieve. Save the melted butter.

Rinse the sushi rice in cold water until the water runs clear. This should require about 10 minutes of agitation and draining.

Add the completely drained sushi rice to the Instant Pot with 2 cups of water.

Set the Instant Pot to Manual on High Pressure for 5 minutes. After it's finished, release the pressure after an additional 5 minutes.

Combine 1 cup of the cooked onions, salt and pepper with the rice. (Reserve the other cooked onions for another recipe or perohe topping)

Unfurl the leaves of the cabbage. Remove the stem of each leaf and stack up the cabbage semi-circles.

Press about 1/4 cup of the rice filling mixture into 2 inch long balls

Roll up the cabbage (instructions above)

Fill the bottom of the Instant Pot with cabbage that was too difficult to work with or tore.

Layer the cabbage rolls on top.

Pour the tomato mixture on top.

Set the Instant Pot to Manual with Low Pressure for 30 minutes.

Allow the pressure to release naturally for 10 minutes then release any remaining pressure