Finely chop the onion, jalapeno, garlic and cilantro.
Transfer to a bowl and season with salt, pepper and red pepper flakes.
Add the remaining ingredients and give it a quick mix.
Taste and adjust seasonings. Refrigerate and serve.
Notes
Not a mayo fan? Use a mix of sour cream and unflavored Greek yogurt instead.
Bump up the flavors of the Chimichurri aioli by using an infused salt like citrus salt or jalapeno salt to season it.
Don't like chopping? Simply add all the ingredients to a food processor and blitz until you get a coarse mixture. You can also add the mayo and other ingredients in the same jar to get that uniform, creamy smooth texture.
Depending on the consistency you're looking for, you can keep the aioli thick or thin it out by adding some Greek yogurt or oil into the mix.
For a bit of color, you can also add some paprika- I used it when I made my Chimichurri Rojo.