Preflop we open JJ UTG and call the BU 3-bet; on A-J-2 rainbow, we should check and then raise the small c-bet rather than just call.
Flop comes A♠ J♣ 2♦ rainbow. This texture is very favorable for BU’s 3-bet range (lots of Ax), so OOP we should start by checking our entire range. Checking with JJ is preferred—our hand is strong but not invulnerable, and checking lets BU c-bet their weaker hands and bluffs while we keep our range protected.
Facing a small 6BB c-bet into 22BB, we’re getting about 4.7:1 and need only ~18% equity, but JJ is far stronger than that. Solver prefers raising here rather than just calling: a large raise (around 90% pot) extracts maximum value from worse Ax and medium pairs, and also makes it harder for BU to continue with hands that are dominated by JJ. Calling is okay but leaves money on the table versus worse made hands and strong draws.