Prep the Onions
Heat the oven to 350°F. Arrange the onions, thyme, and rosemary in a single layer on a rimmed baking sheet. Toss with 2 tablespoons of the olive oil until evenly coated. Season with 1/4 teaspoon salt and a pinch of pepper and toss again. Roast until the onions turn golden but aren't charred, 60 to 75 minutes.
Prep the Croutons
In a large heavy pan, warm the remaining 1 1/2 tablespoons of olive oil over low heat. Add the bread cubes and cook, stirring occasionally, until toasted and golden on all sides, about 10 minutes. Transfer the croutons to a paper towel-lined plate and sprinkle with salt.
Cook the Bacon
Heat a small skillet over medium heat. Cook the bacon, stirring every so often, until crunchy, about 5 minutes. (Optional: with a slotted spoon, put the bacon on top of the kale (add a little of the rendered fat, too, if you like).
Make the Dressing
To make the dressing, using a stand or immersion blender, blend the lemon juice, rice vinegar, capers, anchovies, mustard, and Worcestershire sauce until smooth. With the blender running, pour the olive oil in a thin stream and blend until thoroughly emulsified. Taste and adjust the salt, pepper, and lemon; the dressing should taste vibrant and lemony. (The dressing will keep in a glass jar in the fridge for up to 3 days. Bring to room temp before using.)
Build the Salad
Fold each kale leaf in half along the central rib. With a sharp knife, cut away the rib and discard. Stack a few of the leaves on top of each other, roll them like a cigar, and cut crosswise into 1/8-inch (3mm) ribbons.
Put the kale in a serving bowl, add three-quarters of the dressing, and toss until the leaves are evenly coated.
Add the onions and their juices to the kale and toss with your hands or tongs. Add the croutons, cannellini beans, and ricotta salata. Taste and adjust the seasoning, adding more dressing if the salad is dry.