Preheat oven to 350ºF. Line a baking tray with parchment paper. Spread pecans out evenly making sure none of them touch. Toast in preheated oven for 10 minutes; remove and set aside.
Turn oven up to 450ºF. Prepare a second baking tray with parchment. Cut plums in half, remove pits and then slice into wedges. Toss with 2 Tbsp canola oil and lay out on prepared baking sheet. Roast for 6-8 minutes, turning once.
To make Candied Pecans: stir sugar and water in a small saucepan over medium high heat until sugar is dissolved and comes to a gentle boil. Simmer for 5 minutes, without stirring, until starts to turn a golden colour. Drizzle over pecans and let stand for 20 minutes. When cooled completely, coarsely chop.
To Make Dressing: Stir all ingredients together in a small jar.
Assemble salad by placing spinach leaves on plates. Top with crumbled bacon, red onion, roasted plums and candied pecans. Drizzle with dressing.