Using a blender or pestle and mortar, puree all the curry paste ingredients until they are really smooth.
In a large wide pan, warm the cooking oil and sauté the curry paste, along with the bay leaves and lemongrass until the spices start releasing their aroma.
Slowly pour in the coconut milk and stir to combine.
Next add some sugar and salt to taste and bring the curry to a boil.
When the curry is boiling add the tuna steaks so they are submerged and cooked through and the curry sauce thickens.
Finally add the tamarind water and stir until its evenly distributed.
Serve in a bowl.