Wash the serrano peppers thoroughly and remove their stems. Roughly chop the onion, peel the garlic, and rinse the cilantro. Gather the remaining ingredients so everything is ready before cooking.

Place the serrano peppers, onion, garlic, Mexican oregano, water, white vinegar, salt, cumin, and a few cracks of black pepper into a medium saucepan. Bring the mixture to a gentle boil over medium heat.

Reduce the heat to low and simmer for about 10–12 minutes, or until the peppers become tender and the onion softens. Stir occasionally to ensure everything cooks evenly.

Carefully transfer the cooked mixture to a blender. Add the fresh cilantro and lime juice, then blend at high speed until the sauce becomes completely smooth and creamy. Add a tablespoon or two of water if you prefer a thinner consistency.

Taste the hot sauce and adjust the seasoning if needed by adding a little more salt, lime juice, or black pepper. For an extra smooth texture, strain the sauce through a fine mesh sieve before bottling.

Allow the hot sauce to cool completely before pouring it into a clean glass bottle or airtight jar. Refrigerate for several hours before serving to allow the flavours to fully develop. Shake well before each use.