Chop cauliflower into small florettes and make sure to chop the stems/legs of each florette finely, to avoid large chuncks of cauliflower.
Chop all the other vegetables finely and grate the carrot on a grater.
Heat up the olive oil from tuna can in a large sauteing pan.
Saute onions for 5 minutes or until they are soft and slightly golden.
Add salt and pepper to the onions while they are still cooking.
Add other vegetables and saute till everything is soft and the water is cooked out.
Chop the dill and set a little bit aside, for garnishing later.
In a large bowl, mix the cheeses and creams with chopped dill, leaving about 1/3 of each cheese for topping later.
Once the sauce is ready, add the sauteed vegetables to the sauce.
Flake the tuna apart with fork, and add it into the vegetable and sause mix, combine everything well.
Transfer to the 9 x 9 or similar size baking tray and sprinkle the remaining cheese on top evenly.
Bake for about 20-25 minutes until the top is golden brown.
Sprinkle with extra fresh dill before serving.
Store leftovers in the baking tray covered with plastic wrap after it's completely cool.
Pressure Cooker Method
Follow steps 2-8 from the above instructions in your pressure cooker pot. Do not add the cheeses to the pot before cooking, as they might burn. Instead, add the tuna right to the vegetables.
Close the lid and cook on high pressure for 3 minutes.
Quick-release the pressure and stir in the sauce, allow it to melt in the pressure cooker for a bit, before serving.
Slow Cooker Method
Mix all ingredients except the sauce in your slow cooker.
Cook on low for 3–4 hours.
Add cheddar cheese during the last 30 minutes of cooking.
Notes
Calories, fat, and protein macros may vary slightly depending on the brand of tuna, creams, and cheeses that you use. Carbohydrates should still be the same if you stick to the same amount and types of vegatables as the recipe.