I'm just a single cell; An extremist without a central organelle. What domain am I?

Answer: Prokaryotes

Explanation:

The prokaryotes are the single celled organism which does not contains membrane bound organelles in it.

It also has no nucleus and the genetic material is dissolved in the cytoplasm. The prokayotes are simple organisms that survive only having a single cell.

It has cell wall which protects the prokaryotes from the external environment if the conditions are not favorable or under stress conditions.

Prokaryotes