Begin by slicing the chicken and onions into thin strips and set them aside.
Pour a cup of coconut milk into a heated wok over high heat and allow it to reduce. About 5-7 minutes.
Once the coconut milk has reduced, add in the yellow curry paste, stirring until thoroughly combined with coconut milk.
Let the mixture cook until very fragrant and slightly browning on the bottom, then stir.
Next, pour in the remaining coconut milk and whisk until thoroughly combined with the yellow curry paste.
Add the Tamarind Paste, Fish Sauce, and Brown sugar, stirring it again to ensure the sugar has dissolved and everything has combined.
Pour in the water and bring the curry to a boil.
Once the curry has come to a boil add the sliced chicken, onions, and roasted tomatoes.
Stir to ensure even distribution, reduce heat to medium-low and simmer for 30 minutes or until chicken is cooked through, and onions have softened.
While the curry is simmering, slice the potatoes in half or quarters, depending on which size you prefer, and add them to a bowl of cold water to keep their color.
With about 10 minutes left of the simmering process, add the potatoes to the curry and continue simmering until the potatoes are fork-tender.
Serve with freshly cooked Jasmine rice.