Prepare the matzo crumbs: break the 3 matzo sheets into pieces and pulse in a food processor (or place in a zip-top bag and crush with a rolling pin) into coarse crumbs. Set aside about 2 tablespoons of the crumbs for a light dredge. Drying and crushing matzo gives you a neutral, crisp binder that soaks up moisture without becoming gummy; toasting the crumbs lightly (in the pan for 1–2 minutes) will deepen flavor and improve crunch.

Flake and dry the tuna: drain the canned tuna thoroughly and transfer to a bowl. Use a fork to break into medium flakes. Pat with paper towel to remove excess moisture — removing surface liquid prevents the mixture from becoming soggy and helps the fritters bind and brown better.

Mash the avocado: in a separate bowl, mash the avocado with the lemon juice, minced garlic, salt and pepper until mostly smooth but still slightly chunky. The lemon brightens the avocado and prevents browning while the garlic and seasoning give a flavorful fatty base that complements the tuna.

Build the fritter mixture: add the flaked tuna, shredded cheddar, 2 eggs, onion powder and the larger portion of your matzo crumbs into the avocado bowl. Gently fold to combine — you want enough crumbs and egg to hold the mixture together but not dry it out. The cheddar adds moisture and meltiness that keeps the interior creamy; the eggs act as binder; the matzo provides structure and crispness when cooked.

Rest and adjust seasoning: let the mixture sit 5 minutes so the matzo absorbs some moisture — this makes shaping easier. Taste a small warmed scrap (microwave 10 seconds) and adjust salt, pepper or lemon if needed. Letting the crumbs hydrate slightly is key to stable patties that won’t fall apart.

Shape the fritters: with slightly oiled hands, form the mixture into 12 even patties (about 3 tablespoons each) and gently press them flat to about 3/4" (2 cm) thick. If the mixture is too loose, add another tablespoon of crushed matzo; if too dry, add a teaspoon of water or another small bit of mashed avocado. Uniform size ensures even cooking.

Coat (optional) and preheat skillet: if you reserved crumbs, press each patty briefly into them for a light exterior crust — this step creates an extra-crispy shell. Heat a wide nonstick or stainless-steel skillet over medium heat and add the olive oil. Preheating the pan ensures the oil is hot enough to immediately start browning the fritters (browning yields the Maillard flavors that make them irresistible).

Fry the fritters: place patties in the skillet without overcrowding. Cook 3–4 minutes per side until deep golden brown and firm, easing them up with a spatula to check the color before flipping. Medium heat lets the exterior crisp without burning while giving the center time to heat through and the cheese to melt.

Finish and drain: transfer cooked fritters to a wire rack set over a baking sheet or to paper towels for 1 minute to drain. Resting on a rack preserves crispness; paper towels will absorb excess oil but can slightly steam the underside if stacked.

Serve: arrange 3 fritters per plate and garnish with chopped chives or parsley. Serve with lemon wedges or a quick lemon-yogurt sauce (1/2 cup plain yogurt whisked with 1 tsp lemon zest and a pinch of salt) for a bright counterpoint to the rich, cheesy interior.