Cut the carrots and red onion into roughly 1 cm cubes. Heat a non-stick pan over medium heat and add the vegetables. Cook for 2-3 minutes, stirring frequently, without added fat, until lightly colored. While the vegetables cook, cut the chicken breast fillet into bite-sized cubes.
Transfer the roasted vegetables to a 3.5-liter slow cooker. Add the chicken cubes to the same non-stick pan over medium-high heat and cook for 2-3 minutes, stirring, until lightly browned. Transfer the chicken to the slow cooker.
Bruise the lemongrass stalks using a meat tenderizer and chop finely. Peel the ginger and grate finely using the small holes of a box grater. Place the cashew nuts in a freezer bag and crush roughly with a rolling pin.
In a bowl, combine the coconut milk, red curry paste, tomato paste, soy sauce, turmeric, lemon juice and zest, cashews, lemongrass, and ginger. Season with salt and pepper to taste. Stir in the raisins and pour the mixture over the chicken and vegetables in the slow cooker. Cover and cook on low for 3-5 hours until the chicken reaches an internal temperature of 74°C (165°F).