Cut the cauliflower and broccoli into florets. Peel and dice the red onion. Slice the tomato. Grate the cheddar cheese. Mince the garlic cloves.
Put some water to boil in a pot. Add the florets and boil on medium-heat until tender (about 4-5 minutes). Drain and let completely cool.
Add the olive oil to a frying pan and add the garlic. Cook for a minute and then add the shrimp. Sautee until completely cooked. Put aside and let cool.
In a large bowl, mix together the cooled florets, shrimp, red onion, tomatoes, salt, black pepper, oregano, and cheddar. Mix in the mayonnaise and enjoy!