Preheat the oven to 350°F. Combine the oil, lemon juice, honey, mustard, salt, and pepper in a jar. Seal tightly and shake to emulsify (dressing recipe can be multiplied and kept in the fridge for up to 10 days).
Arrange the pecans on a baking sheet and roast until fragrant and toasty, 7 to 8 minutes. Remove from the oven and transfer the nuts to a plate to cool; roughly chop.
Arrange the lettuce and endive on a large platter, then scatter the tomatoes, avocado, and onions on top. Drizzle with the honey-lemon dressing and top with the pecans.