MOSCOW—The rouble rebounded from a near two-year low and shares in major Russian banks leapt on Tuesday after Britain announced the first but relatively modest sanctions after Moscow recognized two breakaway regions in eastern Ukraine as independent. The rouble on Monday suffered its biggest one-day drop since the outbreak of the COVID-19 pandemic after President Vladimir Putin recognized the two regions as independent, but it regained some ground in volatile trade as the first round of penalties proved to be less harmful than feared. Britain imposed sanctions on five Russian banks and three billionaires but stopped short of targeting major lenders, such as state-controlled Sberbank and VTB. Shares in Russia’s largest lender Sberbank jumped 7.9 percent on the day as of 1517 GMT, while shares in No.2 bank VTB were up 4.7 percent. Other possible sanctions could target major financial institutions, block Russia’s access to electronics supplies, or curb the …