Start your rice cooking. For 3-4 people, I usually use 1 cup rice and 2 cups water, plus 1/2 tsp of salt. Bring to a boil, reduce to a simmer, cover and cook 20-25 minutes. If it gets done before the curry is done just turn the heat off and let it sit a bit.
Heat the oil in a pan at a medium heat.
Cut the chicken into bite size pieces. Obviously you could use pretty much any boneless chicken parts. I'd just bought a bag of chicken tenders by mistake so that's what I used.
Add the onion and garlic to the heated oil and cook for about 10-15 minutes, stirring frequently.
Salt and pepper to taste. Stir in the curry powder and cook another minute.
Add the coconut milk and stir, then stir in the curry paste. (You can use red or green curry paste, depending on how hot you like it. Red works for me.) Cook another few minutes, stirring.
Add the chicken and cook at a simmer until the chicken is done, about 4-5 minutes. Add the tomatoes and cook till heated through. Alternately, you could add peas or bamboo shoots or.... Stir in the basil.