In a medium saute pan over medium heat add oil. When oil is hot add onions and cook, stirring occasionally until onions release their natural sugar and become golden brown, about 20 minutes.
To make dressing: In a small jar or pint container with a lid add mustard, honey, vinegar, oil, salt and pepper. Place top on container and shake to combine.
In a large mixing bowl add spinach, roasted pepper, beans, feta, tuna and 2 tablespoons dressing. Toss to combine. Garnish with caramelized onion, orange segments and toasted almonds.