1. Heat a large skillet over medium-high heat. Add oil to pan; swirl to coat. Add onion and garlic to pan; sauté 5 minutes, stirring frequently. Reduce heat to medium-low; cook 35 minutes or until very tender and caramelized, stirring occasionally. Add cream cheese to pan, and stir to combine. Remove from heat; stir in mayonnaise and the remaining ingredients. Serve at room temperature or chilled.
Make-ahead tip: Refrigerate the spread (or its components) up to two days ahead.