1Cut jalapeños in half lengthwise and remove seeds; place in large bowl. Add onion and carrots. Stir in kosher salt. Let stand 1 hour at room temperature, stirring occasionally. Strain vegetables and reserve liquid. Set aside.
2Place vinegar, water, cumin seeds, oregano, peppercorns and bay leaf in blender container. Blend on HIGH until completely smooth. Set aside.
3Heat oil in large saucepan on medium-high heat until shimmering. Add vegetables; cook and stir 5 minutes until softened. Add garlic; cook 2 minutes longer.
4Stir in reserved vegetable liquid and vinegar mixture. Bring to simmer; cook 8 to 10 minutes. Remove from heat and cool completely. Store in airtight container in refrigerator up to 2 months.