Take the husks. Take the husks of the corn by pulling on it in strips, taking special care to not tear them.
Place corn in wet towel. Wet a paper towel and then place them in and fold the paper towel so that it's closed.
Crush corn. Use the knife to cut away the corn kernels and then throw away the center. Run them through a food processor until you get a rough, sort of shaggy mixture.
Cut vegetables. Chop up the onion into small pieces and mince the jalapeño and garlic so that you are then able to mix them all together well, along with the corn, in the mixing bowl.
Mix the masa. Now add the masa and baking powder with a bit of salt(the amount is totally up to you, just make sure to not put too little if you really want to set off the flavoring), and then mix it all together until you end up with a thick batter.
Fill the batter. Now take the husks out of the paper towel and spread one out on a spacious work surface so that you're able to fill in a decent amount of the batter that you just prepared. You should be able to cover the batter and fold them, making sure to leave one end open so that it cooks right. If you need to you can use numerous husks so that they cover the batter. The last thing that you want is to end up leaving batter hanging out. Repeat as necessary.
Cook the tamales. Now place them in the steamer and cook them for an hour and 15 minutes. You might need to keep them in longer until they are soft and plump.