In a medium saucepan, heat the olive oil over medium heat. Add the chopped onion and serrano pepper, and sauté until the onion becomes translucent and the pepper softens.
Add the minced garlic and adobo sauce to the saucepan, stirring well to incorporate the flavors. Cook for an additional minute until the garlic becomes fragrant.
Add the raspberries, apple cider vinegar, brown sugar, granulated sugar, and salt to the saucepan. Stir gently to combine all the ingredients.
Bring the mixture to a boil over medium-high heat, then reduce the heat to low and simmer for about 15-20 minutes, or until the raspberries break down and the sauce thickens to your desired consistency. Stir occasionally to prevent the sauce from sticking to the pan.
Once the sauce has thickened, remove it from the heat and let it cool slightly. Transfer the sauce to a blender or use an immersion blender to puree until smooth. If you prefer a chunkier sauce, you can skip this step.