Blazes will spawn around a spawner if there is a light level of 11 or lower (lower half of their body). When you remove the light sources within the cage, you may need a potion of Fire Resistance to survive a swarm of blazes.

How to Enter the Command

1
Open the Chat Window. The easiest way to run a command in Minecraft is within the chat window.
2
Type the Command. In this example, we are going to summon a fireball in Minecraft Java Edition (PC/Mac) 1.20 with the following command: /summon fireball ~ ~1 ~