Saute onions in olive oil until soft, not brown. Remove from heat.
Mix in everything else except grape leaves and lemon, cool.
If using fresh grape leaves, blanch quickly in boiling water. If using canned or jarred, no need for this step. Rinse canned or jarred leaves to remove brine.
Lay out one leaf, pointy side up, shiny side down, cutting off stem.
Put a teaspoon of filling in the center, in a line. Fold up bottom of leaf to cover filling and then fold in sides and roll up to point of leaf. Don't roll too tightly because rice will expand. Similar to rolling a burrito or cigar.
Dolma can be cooked in a double boiler to prevent scorching, or line a pot with broken leaves. Place all rolls in pot lined up neatly and stacked up until all are in pot. Cover with a plate to prevent floating.
Squeeze 1 lemon into pot and add 2 cups of water.
Cook over low heat for about an hour and check. If liquid is not absorbed keep cooking until no more liquid remains.
Cool in pot without removing plate. Refrigerate until chilled and serve with lemon wedges.