Achiote paste can be found in the spice section, or meat section, in Mexican markets. I also saw a recipe on Zaar foor it. This is a great marinade for skirt steak, but is also good with pork and chicken.
Another great recipe from Mark Bittman. If you want to add a little heat, use ground cayenne. You can also add diced boneless chicken during the last 10 minutes of cooking.
You can used canned drained tomatoes in place of fresh.
You will need a large, sterilized, wide mouth bottle or jar for this. The tequila will need to stand 1 week before using. After you drink the tequila, you can serve the fruit with ice cream or warm with butter and cinnamon. Yum!!!