To make the candied pecans: Line a baking sheet with parchment paper, set a wire rack (the gridded kind) on top, and set aside.
In a medium saucepan, combine 1⁄2 cup sugar with the water and mash with a fork until the sugar is fully moistened. Place the pan over high heat and cook until the sugar dissolves and turns a rich amber color, swirling the pan occasionally but resisting the temptation to stir. (It will take 5–7 minutes, but don’t rush it. You want a beautiful deep brown color.) Remove the pan from the heat and carefully add the butter, then stir until it melts. Add the pecans, stir to coat completely, and spread them on the wire rack.
In a small bowl, stir together the remaining 1 Tbsp. sugar with the salt, cinnamon, and cayenne to taste. Sprinkle this mixture evenly over the pecans and let cool completely.
To make the vinaigrette: In a blender, blend 1 cup of the olive oil, vinegar, Dijon, maple syrup, salt, and pepper until smooth. Season to taste with additional oil (if the dressing is too sharp for you), salt, and pepper, and set aside.
To make the Spiced Pickled Red Onions: Halve and thinly slice the red onion pole to pole, break apart the pieces, and stuff them all into a 4-cup mason jar or similar container. In a small saucepan, combine vinegar, water, sugar, salt, red pepper flakes, and mustard powder, and bring to a boil, whisking to dissolve the sugar and salt. Carefully pour the mixture over the onions, press any that are sticking out down into the liquid, and cover. Let cool to room temperature, then use immediately or refrigerate for up to 3 weeks.
To assemble the salad: Pile the spinach and kale into a large serving bowl and top with the pecans, onions, cherries, and cheese. Dress the salad to taste with the vinaigrette, toss well, and serve. Store any unused vinaigrette in the refrigerator, covered, for up to 1 week.