Start by chopping up the onion into small pieces.
Cut the jalapeño peppers in half and scoop out the seeds with a spoon.
Now, bring a saucepan of water to a boil.
Add the chopped onion and sliced jalapeños to the boiling water. Let them cook until they become fork-tender, which should take about 10 minutes.
Once the onions and jalapeños are cooked, strain them to remove the water.
Place the cooked onions, jalapeños, garlic cloves, salt, and grape seed oil (or corn oil) into a blender.
Blend everything together for about 3-4 minutes until you achieve a creamy consistency. You want all the ingredients to combine smoothly.
After blending, taste the sauce and adjust the salt if needed. You can also add extra jalapenos if you prefer it spicy.
Now, transfer the creamy jalapeño sauce to a container or jar with a lid.
Refrigerate the sauce to chill it. Chilling will help the flavors meld together and make the sauce even more delicious.
Once it's cold, your creamy jalapeño sauce is ready to enjoy!