Purée 1 medium onion, coarsely chopped, 1 plum tomato, coarsely chopped, 3 garlic cloves, one 1″ piece ginger, scrubbed, and 2 red Thai chiles or 1 Fresno chile in a blender until smooth.
Heat 1 Tbsp. extra-virgin olive oil in a large deep skillet over medium. Add onion mixture and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt. Cook, stirring occasionally, until moisture is evaporated and mixture is paste-like in consistency and beginning to stick to bottom of skillet, 12–16 minutes.
Stir in ½ tsp. ground coriander, ½ tsp. ground cumin, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt. Pour in one 13.5-oz. can unsweetened coconut milk and 2 cups water; stir to combine. Increase heat to medium-high and bring to a boil. Add 1 medium sweet potato, peeled, sliced into ¼”-thick rounds, and cook, stirring occasionally, until tender, 10–12 minutes.
Add 1 large bunch Swiss chard or Tuscan kale, ribs and stems removed, leaves coarsely chopped, and two 15-oz. cans butter, gigante, or cannellini beans, rinsed, and cook, stirring occasionally, until chard is wilted, about 4 minutes. Remove from heat and stir in 2 Tbsp. fresh lemon juice. Taste and add more kosher salt and/or lemon juice if needed.
Meanwhile, heat 1 Tbsp. extra-virgin olive oil in a large cast-iron skillet over medium-high. Working in 2 batches and adding 1 Tbsp. extra-virgin olive oil between batches, fry 1 baguette, sliced on a diagonal 1″ thick, until golden, about 2 minutes per side. Set aside.
Divide stew among bowls. Season with flaky sea salt and drizzle with more extra-virgin olive oil. Serve with toasts.