Mince the garlic and set aside.
20 garlic cloves
Remove the stems from the árbol chiles and gently roll the chiles between your fingers to remove the seeds. Discard the seeds.
2 arbol chiles
Heat a medium cast-iron skillet over medium heat for about 3 minutes. Add the black peppercorns, oregano, and chiles; toast, shaking the pan, until fragrant, about 15 seconds.
½ teaspoon black peppercorns, ½ teaspoon dried Mexican oregano
Remove from the heat, transfer to a spice grinder, and grind to a fine powder. Or use a mortar and pestle to grind them.
Set a 1-quart saucepan over medium heat and add the olive oil and garlic. Cook until the garlic begins to turn slight golden, stirring often to prevent it from sticking to the pan.
1 cup extra virgin olive oil, 20 garlic cloves
Add the orange juice and tomato, followed by the ground spices and stir to combine. Continue to cook until the tomato has softened and cooked throughly, about 2 minutes.
1 orange, juiced., 1 medium ripe plum tomato
Remove the mixture from the heat and let cool to room temperature. Transfer to a container and refrigerate until ready to use.
Store it in the refrigerator in an airtight container for up to 1 month. Makes about 1 ½ cups.